diff --git a/backend/task_scheduler/app/celery_app.py b/backend/task_scheduler/app/celery_app.py
index d0e8971..47f0cab 100644
--- a/backend/task_scheduler/app/celery_app.py
+++ b/backend/task_scheduler/app/celery_app.py
@@ -13,6 +13,7 @@ import sys
 import logging
 
 from celery import Celery
+from celery.schedules import crontab
 
 # 确保 shared 模块可导入
 sys.path.insert(0, os.path.join(os.path.dirname(__file__), "../.."))
@@ -42,6 +43,10 @@ celery_app.conf.update(
             "task": "task_scheduler.app.tasks.signin_tasks.check_and_run_due_tasks",
             "schedule": 60.0,  # 每分钟检查一次（轻量查询，只在到期前 5 分钟才真正提交）
         },
+        "cleanup-old-logs": {
+            "task": "task_scheduler.app.tasks.signin_tasks.cleanup_old_signin_logs",
+            "schedule": crontab(hour=3, minute=0),  # 每天凌晨 3 点
+        },
     },
 )
 
diff --git a/backend/task_scheduler/app/tasks/signin_tasks.py b/backend/task_scheduler/app/tasks/signin_tasks.py
index 32de6bf..4a4618d 100644
--- a/backend/task_scheduler/app/tasks/signin_tasks.py
+++ b/backend/task_scheduler/app/tasks/signin_tasks.py
@@ -396,3 +396,59 @@ async def _do_single_signin(cookies: Dict[str, str], topic: dict) -> dict:
                 return {"status": "failed", "message": f"code={code}, msg={msg}"}
     except Exception as e:
         return {"status": "failed", "message": str(e)}
+
+
+# =============== 日志清理 ===============
+
+# 保留天数，可通过环境变量覆盖
+SIGNIN_LOG_RETAIN_DAYS = int(os.getenv("SIGNIN_LOG_RETAIN_DAYS", "30"))
+# 每批删除条数，避免长时间锁表
+CLEANUP_BATCH_SIZE = 1000
+
+
+@celery_app.task
+def cleanup_old_signin_logs():
+    """
+    清理超过 N 天的签到日志。
+    分批删除，每批最多 CLEANUP_BATCH_SIZE 条，避免锁表。
+    """
+    logger.info(f"🧹 开始清理 {SIGNIN_LOG_RETAIN_DAYS} 天前的签到日志...")
+    return _run_async(_async_cleanup())
+
+
+async def _async_cleanup():
+    from sqlalchemy import delete, func
+
+    cutoff = datetime.now() - timedelta(days=SIGNIN_LOG_RETAIN_DAYS)
+    total_deleted = 0
+
+    SessionFactory, eng = _make_session()
+    try:
+        async with SessionFactory() as session:
+            while True:
+                # 分批删除：先查出一批 id，再按 id 删除
+                stmt = (
+                    select(SigninLog.id)
+                    .where(SigninLog.signed_at < cutoff)
+                    .limit(CLEANUP_BATCH_SIZE)
+                )
+                result = await session.execute(stmt)
+                ids = [row[0] for row in result.all()]
+
+                if not ids:
+                    break
+
+                del_stmt = delete(SigninLog).where(SigninLog.id.in_(ids))
+                await session.execute(del_stmt)
+                await session.commit()
+                total_deleted += len(ids)
+                logger.info(f"🧹 已删除 {total_deleted} 条...")
+
+                # 如果本批不满，说明已经删完
+                if len(ids) < CLEANUP_BATCH_SIZE:
+                    break
+    finally:
+        await eng.dispose()
+
+    logger.info(f"✅ 日志清理完成，共删除 {total_deleted} 条（截止 {cutoff.strftime('%Y-%m-%d')}）")
+    return {"deleted": total_deleted, "cutoff": cutoff.isoformat()}