diff --git a/app/src/main/java/io/legado/app/help/config/AppConfig.kt b/app/src/main/java/io/legado/app/help/config/AppConfig.kt
index 0555a3734d..d2e0c6fa2c 100644
--- a/app/src/main/java/io/legado/app/help/config/AppConfig.kt
+++ b/app/src/main/java/io/legado/app/help/config/AppConfig.kt
@@ -834,7 +834,7 @@ object AppConfig : SharedPreferences.OnSharedPreferenceChangeListener {
     val syncEnabled get() = appCtx.getPrefBoolean(PreferKey.syncEnabled, false)
 
     val syncInterval: Int
-        get() = appCtx.getPrefString(PreferKey.syncInterval)?.toIntOrNull() ?: 15
+        get() = appCtx.getPrefString(PreferKey.syncInterval)?.toIntOrNull() ?: 5
 
     /** 需要同步的数据类型 */
     val syncDataTypes: Set<String>
diff --git a/app/src/main/java/io/legado/app/help/sync/worker/SyncWorker.kt b/app/src/main/java/io/legado/app/help/sync/worker/SyncWorker.kt
index eb0ca0d54e..cf6e539383 100644
--- a/app/src/main/java/io/legado/app/help/sync/worker/SyncWorker.kt
+++ b/app/src/main/java/io/legado/app/help/sync/worker/SyncWorker.kt
@@ -14,10 +14,11 @@ class SyncWorker(
 ) : CoroutineWorker(appContext, params) {
 
     override suspend fun doWork(): Result {
-        return if (SyncManager.syncWorker()) {
-            Result.success()
-        } else {
-            Result.retry()
+        val ok = SyncManager.syncWorker()
+        if (ok) {
+            WorkManagerHelper.scheduleNext(applicationContext)
+            return Result.success()
         }
+        return Result.retry()
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/io/legado/app/help/sync/worker/WorkManagerHelper.kt b/app/src/main/java/io/legado/app/help/sync/worker/WorkManagerHelper.kt
index e2fa1e8dab..3816fc8db9 100644
--- a/app/src/main/java/io/legado/app/help/sync/worker/WorkManagerHelper.kt
+++ b/app/src/main/java/io/legado/app/help/sync/worker/WorkManagerHelper.kt
@@ -3,7 +3,9 @@ package io.legado.app.help.sync.worker
 import android.content.Context
 import androidx.work.Constraints
 import androidx.work.ExistingPeriodicWorkPolicy
+import androidx.work.ExistingWorkPolicy
 import androidx.work.NetworkType
+import androidx.work.OneTimeWorkRequestBuilder
 import androidx.work.PeriodicWorkRequestBuilder
 import androidx.work.WorkManager
 import io.legado.app.help.sync.SyncConfig
@@ -14,34 +16,70 @@ import java.util.concurrent.TimeUnit
  */
 object WorkManagerHelper {
 
-    private const val UNIQUE_NAME = "sync_periodic_work"
+    private const val UNIQUE_PERIODIC = "sync_periodic_work"
+    private const val UNIQUE_LOOP = "sync_loop_work"
 
-    /** 最短周期(分钟), WorkManager 周期任务下限为 15 分钟 */
-    private const val MIN_INTERVAL = 15L
+    /** WorkManager 周期任务最短周期(分钟), 低于此值用一次性任务自续期循环 */
+    private const val MIN_PERIODIC = 15L
 
     /**
      * 按设置调度周期同步, 设置变更时重新调度
+     * 间隔 >= 15 分钟: PeriodicWorkRequest; < 15 分钟(即时/5/10): OneTimeWorkRequest 自续期循环
      */
     fun schedule(context: Context) {
         if (!SyncConfig.enabled) {
             cancel(context)
             return
         }
-        val interval = SyncConfig.intervalMinutes.toLong().coerceAtLeast(MIN_INTERVAL)
+        val interval = SyncConfig.intervalMinutes.toLong()
+        val wm = WorkManager.getInstance(context)
+        if (interval >= MIN_PERIODIC) {
+            wm.cancelUniqueWork(UNIQUE_LOOP)
+            val constraints = Constraints.Builder()
+                .setRequiredNetworkType(NetworkType.CONNECTED)
+                .build()
+            val request = PeriodicWorkRequestBuilder<SyncWorker>(interval, TimeUnit.MINUTES)
+                .setConstraints(constraints)
+                .build()
+            wm.enqueueUniquePeriodicWork(
+                UNIQUE_PERIODIC,
+                ExistingPeriodicWorkPolicy.UPDATE,
+                request
+            )
+        } else {
+            wm.cancelUniqueWork(UNIQUE_PERIODIC)
+            enqueueLoop(wm)
+        }
+    }
+
+    /**
+     * 续期下一次循环同步, 由 SyncWorker 同步成功后调用
+     */
+    fun scheduleNext(context: Context) {
+        if (!SyncConfig.enabled) return
+        if (SyncConfig.intervalMinutes >= MIN_PERIODIC) return
+        enqueueLoop(WorkManager.getInstance(context))
+    }
+
+    private fun enqueueLoop(wm: WorkManager) {
+        val interval = SyncConfig.intervalMinutes.toLong().coerceAtLeast(0)
         val constraints = Constraints.Builder()
             .setRequiredNetworkType(NetworkType.CONNECTED)
             .build()
-        val request = PeriodicWorkRequestBuilder<SyncWorker>(interval, TimeUnit.MINUTES)
+        val request = OneTimeWorkRequestBuilder<SyncWorker>()
+            .setInitialDelay(interval, TimeUnit.MINUTES)
             .setConstraints(constraints)
             .build()
-        WorkManager.getInstance(context).enqueueUniquePeriodicWork(
-            UNIQUE_NAME,
-            ExistingPeriodicWorkPolicy.UPDATE,
+        wm.enqueueUniqueWork(
+            UNIQUE_LOOP,
+            ExistingWorkPolicy.REPLACE,
             request
         )
     }
 
     fun cancel(context: Context) {
-        WorkManager.getInstance(context).cancelUniqueWork(UNIQUE_NAME)
+        val wm = WorkManager.getInstance(context)
+        wm.cancelUniqueWork(UNIQUE_PERIODIC)
+        wm.cancelUniqueWork(UNIQUE_LOOP)
     }
 }
\ No newline at end of file
diff --git a/app/src/main/res/values-zh-rHK/strings.xml b/app/src/main/res/values-zh-rHK/strings.xml
index 10d813b091..db4ccaafd8 100644
--- a/app/src/main/res/values-zh-rHK/strings.xml
+++ b/app/src/main/res/values-zh-rHK/strings.xml
@@ -817,6 +817,47 @@
     <string name="sync_book_progress_s">進入退出閱讀介面時同步閱讀進度</string>
     <string name="sync_book_progress_plus_t">同步增強</string>
     <string name="sync_book_progress_plus_s">重新進入頁面（息屏、從背景返回等）或網路恢復可用時同步雲端進度，同步新進度時會詢問</string>
+    <string name="sync_setting">增量同步</string>
+    <string name="sync_setting_s">通過 WebDAV 多端增量同步</string>
+    <string name="sync_enable">開啟同步</string>
+    <string name="sync_enable_s">定時以及應用程式啟動/退出時同步</string>
+    <string name="sync_interval">同步間隔</string>
+    <string name="sync_interval_s">最小間隔為即時（持續同步）</string>
+    <string name="sync_interval_immediate">即時</string>
+    <string name="sync_interval_5m">5分鐘</string>
+    <string name="sync_interval_10m">10分鐘</string>
+    <string name="sync_interval_30m">30分鐘</string>
+    <string name="sync_data_types">同步資料類型</string>
+    <string name="sync_data_types_s">選擇要同步的資料</string>
+    <string name="sync_conflict_mode">預設衝突策略</string>
+    <string name="sync_conflict_mode_s">本地和雲端都發生變化時採用的策略</string>
+    <string name="sync_actions">同步操作</string>
+    <string name="sync_now">立即同步</string>
+    <string name="sync_now_s">立即拉取並推送變更</string>
+    <string name="sync_enable_tip">請先開啟同步</string>
+    <string name="sync_last_status">上次同步狀態</string>
+    <string name="sync_last_status_s">暫無同步記錄</string>
+    <string name="sync_conflicts">衝突列表</string>
+    <string name="sync_conflicts_s">查看並解決同步衝突</string>
+    <string name="sync_type_books">書架（中繼資料）</string>
+    <string name="sync_type_bookmarks">書籤</string>
+    <string name="sync_type_bookgroups">書籍分組</string>
+    <string name="sync_type_readrecords">閱讀記錄</string>
+    <string name="sync_type_readconfigs">閱讀設定</string>
+    <string name="sync_conflict_manual">手動處理</string>
+    <string name="sync_conflict_keep_local">保留本地</string>
+    <string name="sync_conflict_keep_cloud">保留雲端</string>
+    <string name="sync_conflict">同步衝突</string>
+    <string name="conflict_keep_local">使用本地</string>
+    <string name="conflict_keep_cloud">使用雲端</string>
+    <string name="conflict_keep_both">保留兩者</string>
+    <string name="conflict_apply_all_local">全部使用本地</string>
+    <string name="conflict_apply_all_cloud">全部使用雲端</string>
+    <string name="conflict_clear_resolved">清除已解決</string>
+    <string name="conflict_empty">暫無待解決衝突</string>
+    <string name="conflict_record_key">記錄：%1$s</string>
+    <string name="conflict_resolved">已解決</string>
+    <string name="conflict_resolve_success">衝突已解決</string>
     <string name="create_bookmark_error">建立書籤失敗</string>
     <string name="single_url">單URL</string>
     <string name="export_bookshelf">導出書單</string>
diff --git a/app/src/main/res/values-zh-rTW/strings.xml b/app/src/main/res/values-zh-rTW/strings.xml
index 9db72401f2..3d665b7f1e 100644
--- a/app/src/main/res/values-zh-rTW/strings.xml
+++ b/app/src/main/res/values-zh-rTW/strings.xml
@@ -820,6 +820,47 @@
     <string name="sync_book_progress_s">進入退出閱讀介面時同步閱讀進度</string>
     <string name="sync_book_progress_plus_t">同步增強</string>
     <string name="sync_book_progress_plus_s">重新進入頁面（息屏、從背景返回等）或網路恢復可用時同步雲端進度，同步新進度時會詢問</string>
+    <string name="sync_setting">增量同步</string>
+    <string name="sync_setting_s">透過 WebDAV 多端增量同步</string>
+    <string name="sync_enable">開啟同步</string>
+    <string name="sync_enable_s">定時以及應用程式啟動/退出時同步</string>
+    <string name="sync_interval">同步間隔</string>
+    <string name="sync_interval_s">最小間隔為即時（持續同步）</string>
+    <string name="sync_interval_immediate">即時</string>
+    <string name="sync_interval_5m">5分鐘</string>
+    <string name="sync_interval_10m">10分鐘</string>
+    <string name="sync_interval_30m">30分鐘</string>
+    <string name="sync_data_types">同步資料類型</string>
+    <string name="sync_data_types_s">選擇要同步的資料</string>
+    <string name="sync_conflict_mode">預設衝突策略</string>
+    <string name="sync_conflict_mode_s">本地和雲端都發生變化時採用的策略</string>
+    <string name="sync_actions">同步操作</string>
+    <string name="sync_now">立即同步</string>
+    <string name="sync_now_s">立即拉取並推送變更</string>
+    <string name="sync_enable_tip">請先開啟同步</string>
+    <string name="sync_last_status">上次同步狀態</string>
+    <string name="sync_last_status_s">暫無同步記錄</string>
+    <string name="sync_conflicts">衝突列表</string>
+    <string name="sync_conflicts_s">查看並解決同步衝突</string>
+    <string name="sync_type_books">書架（中繼資料）</string>
+    <string name="sync_type_bookmarks">書籤</string>
+    <string name="sync_type_bookgroups">書籍分組</string>
+    <string name="sync_type_readrecords">閱讀記錄</string>
+    <string name="sync_type_readconfigs">閱讀設定</string>
+    <string name="sync_conflict_manual">手動處理</string>
+    <string name="sync_conflict_keep_local">保留本地</string>
+    <string name="sync_conflict_keep_cloud">保留雲端</string>
+    <string name="sync_conflict">同步衝突</string>
+    <string name="conflict_keep_local">使用本地</string>
+    <string name="conflict_keep_cloud">使用雲端</string>
+    <string name="conflict_keep_both">保留兩者</string>
+    <string name="conflict_apply_all_local">全部使用本地</string>
+    <string name="conflict_apply_all_cloud">全部使用雲端</string>
+    <string name="conflict_clear_resolved">清除已解決</string>
+    <string name="conflict_empty">暫無待解決衝突</string>
+    <string name="conflict_record_key">記錄：%1$s</string>
+    <string name="conflict_resolved">已解決</string>
+    <string name="conflict_resolve_success">衝突已解決</string>
     <string name="create_bookmark_error">建立書籤失敗</string>
     <string name="single_url">單URL</string>
     <string name="export_bookshelf">匯出書單</string>
diff --git a/app/src/main/res/values-zh/strings.xml b/app/src/main/res/values-zh/strings.xml
index 86f7e5a05c..f2cbbd3357 100644
--- a/app/src/main/res/values-zh/strings.xml
+++ b/app/src/main/res/values-zh/strings.xml
@@ -830,6 +830,47 @@
     <string name="sync_book_progress_s">进入退出阅读界面时同步阅读进度</string>
     <string name="sync_book_progress_plus_t">同步增强</string>
     <string name="sync_book_progress_plus_s">重新进入页面（息屏、后台返回等）或者网络变为可用时同步云端进度，同步新进度会询问</string>
+    <string name="sync_setting">增量同步</string>
+    <string name="sync_setting_s">通过 WebDAV 多端增量同步</string>
+    <string name="sync_enable">开启同步</string>
+    <string name="sync_enable_s">定时以及应用启动/退出时同步</string>
+    <string name="sync_interval">同步间隔</string>
+    <string name="sync_interval_s">最小间隔为即时（持续同步）</string>
+    <string name="sync_interval_immediate">即时</string>
+    <string name="sync_interval_5m">5分钟</string>
+    <string name="sync_interval_10m">10分钟</string>
+    <string name="sync_interval_30m">30分钟</string>
+    <string name="sync_data_types">同步数据类型</string>
+    <string name="sync_data_types_s">选择要同步的数据</string>
+    <string name="sync_conflict_mode">默认冲突策略</string>
+    <string name="sync_conflict_mode_s">本地和云端都发生变化时采用的策略</string>
+    <string name="sync_actions">同步操作</string>
+    <string name="sync_now">立即同步</string>
+    <string name="sync_now_s">立即拉取并推送变更</string>
+    <string name="sync_enable_tip">请先开启同步</string>
+    <string name="sync_last_status">上次同步状态</string>
+    <string name="sync_last_status_s">暂无同步记录</string>
+    <string name="sync_conflicts">冲突列表</string>
+    <string name="sync_conflicts_s">查看并解决同步冲突</string>
+    <string name="sync_type_books">书架（元数据）</string>
+    <string name="sync_type_bookmarks">书签</string>
+    <string name="sync_type_bookgroups">书籍分组</string>
+    <string name="sync_type_readrecords">阅读记录</string>
+    <string name="sync_type_readconfigs">阅读设置</string>
+    <string name="sync_conflict_manual">手动处理</string>
+    <string name="sync_conflict_keep_local">保留本地</string>
+    <string name="sync_conflict_keep_cloud">保留云端</string>
+    <string name="sync_conflict">同步冲突</string>
+    <string name="conflict_keep_local">使用本地</string>
+    <string name="conflict_keep_cloud">使用云端</string>
+    <string name="conflict_keep_both">保留两者</string>
+    <string name="conflict_apply_all_local">全部使用本地</string>
+    <string name="conflict_apply_all_cloud">全部使用云端</string>
+    <string name="conflict_clear_resolved">清除已解决</string>
+    <string name="conflict_empty">暂无待解决冲突</string>
+    <string name="conflict_record_key">记录：%1$s</string>
+    <string name="conflict_resolved">已解决</string>
+    <string name="conflict_resolve_success">冲突已解决</string>
     <string name="create_bookmark_error">创建书签失败</string>
     <string name="single_url">单 URL</string>
     <string name="export_bookshelf">导出书单</string>
diff --git a/app/src/main/res/values/arrays.xml b/app/src/main/res/values/arrays.xml
index e67d445674..b7cae5360c 100644
--- a/app/src/main/res/values/arrays.xml
+++ b/app/src/main/res/values/arrays.xml
@@ -209,21 +209,17 @@
 	</string-array>
 
 	<string-array name="sync_interval">
-		<item>15 minutes</item>
-		<item>30 minutes</item>
-		<item>1 hour</item>
-		<item>3 hours</item>
-		<item>6 hours</item>
-		<item>12 hours</item>
+		<item>@string/sync_interval_immediate</item>
+		<item>@string/sync_interval_5m</item>
+		<item>@string/sync_interval_10m</item>
+		<item>@string/sync_interval_30m</item>
 	</string-array>
 
 	<string-array name="sync_interval_values">
-		<item>15</item>
+		<item>0</item>
+		<item>5</item>
+		<item>10</item>
 		<item>30</item>
-		<item>60</item>
-		<item>180</item>
-		<item>360</item>
-		<item>720</item>
 	</string-array>
 
 	<string-array name="sync_data_types">
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 92e08a60bd..d548976504 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -837,7 +837,11 @@
     <string name="sync_enable">Enable sync</string>
     <string name="sync_enable_s">Synchronize periodically and on app start / exit</string>
     <string name="sync_interval">Sync interval</string>
-    <string name="sync_interval_s">Minimum interval is 15 minutes</string>
+    <string name="sync_interval_s">Minimum interval: immediately (syncs continuously)</string>
+    <string name="sync_interval_immediate">Immediately</string>
+    <string name="sync_interval_5m">5 minutes</string>
+    <string name="sync_interval_10m">10 minutes</string>
+    <string name="sync_interval_30m">30 minutes</string>
     <string name="sync_data_types">Sync data types</string>
     <string name="sync_data_types_s">Select which data to synchronize</string>
     <string name="sync_conflict_mode">Default conflict strategy</string>
diff --git a/app/src/main/res/xml/pref_config_sync.xml b/app/src/main/res/xml/pref_config_sync.xml
index 26c9944d81..b54da5ea5c 100644
--- a/app/src/main/res/xml/pref_config_sync.xml
+++ b/app/src/main/res/xml/pref_config_sync.xml
@@ -19,7 +19,7 @@
             app:iconSpaceReserved="false" />
 
         <io.legado.app.lib.prefs.NameListPreference
-            android:defaultValue="15"
+            android:defaultValue="5"
             android:entries="@array/sync_interval"
             android:entryValues="@array/sync_interval_values"
             android:key="syncInterval"
diff --git a/plan-V1.md b/plan-V1.md
index 6636412426..578b3f8deb 100644
--- a/plan-V1.md
+++ b/plan-V1.md
@@ -113,7 +113,7 @@ sync/tombstones/<table>_<key>.json         { deleted:true, deletedAt }
 ## 6. 调度与生命周期
 
 - 新增 `androidx.work:work-runtime-ktx` 到 `gradle/libs.versions.toml` 与 `app/build.gradle`。
-- `sync/worker/SyncWorker.kt`：`CoroutineWorker`，`PeriodicWorkRequest`（最短 15min，用户间隔取 >=15min 档位）+ `NetworkType.CONNECTED` 约束；设置变更时重排。
+- `sync/worker/SyncWorker.kt`：`CoroutineWorker`，间隔档位为 **即时/5分钟/10分钟/30分钟**；`>=15min` 用 `PeriodicWorkRequest`（WorkManager 周期任务下限）+ `NetworkType.CONNECTED` 约束，`<15min`（即时/5/10）用 `OneTimeWorkRequest` 自续期循环（Worker 同步成功后 `scheduleNext` 续排下一轮，即时=连续同步）；设置变更时重排。
 - `App.kt:123` 处同步逻辑改为 `SyncManager.pullOnly()`（替换/并列现有 `downloadAllBookProgress`）。
 - 进程退出推送：用 `ProcessLifecycleOwner` observer 或新建 `SyncLifecycleObserver` 在 `onStop` 触发 `pushOnly()`。
 - 手动同步按钮调用 `syncNow()`。
@@ -170,7 +170,8 @@ M2 — 同步引擎核心
 M3 — 调度
 - WorkManager 依赖已加（gradle/libs.versions.toml work=2.10.0、app/build.gradle work-runtime-ktx + lifecycle-process）
 - SyncWorker.kt：CoroutineWorker，调 SyncManager.syncWorker()，失败返回 retry
-- WorkManagerHelper.kt：PeriodicWorkRequest，间隔>=15min，NetworkType.CONNECTED 约束，UPDATE 策略重排/取消
+- WorkManagerHelper.kt：间隔>=15min 用 PeriodicWorkRequest，<15min（即时/5/10）用 OneTimeWorkRequest 自续期循环（scheduleNext），NetworkType.CONNECTED 约束，UPDATE 策略重排/取消
+- 同步间隔档位改为 即时(0)/5/10/30 分钟（values/arrays.xml + 四语言 strings），默认 5 分钟；WorkManagerHelper 双调度路径（periodic + loop）
 - SyncLifecycleObserver.kt：ProcessLifecycleOwner ON_STOP → SyncManager.syncOnStop()
 - App.kt：onCreate 调度周期任务、注册生命周期观察者、启动后 syncOnStart()
 - AppConfig：syncEnabled/syncInterval 变更时重排周期任务
@@ -185,7 +186,3 @@ M4 — UI/设置
 - ConflictResolver 新增 keepBoth()（两端各留一份、消除冲突）
 - SyncConflictDao 新增 observeAll()/pendingCount
 - 字符串/数组资源、AndroidManifest 注册 ConflictActivity
-
-### 未完成
-M5 — 测试
-- 冲突算法单测、迁移 androidTest、双模拟器同步演练未做
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