diff --git a/backend/app/main.py b/backend/app/main.py
index 83d8028..508696e 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -4,7 +4,8 @@ from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
 from app.config import settings
-from app.database import Base, engine
+from app.database import Base, engine, SessionLocal
+from app.models import Mindmap
 from app.routers import chat, mindmaps
 
 logging.basicConfig(
@@ -15,6 +16,15 @@ logger = logging.getLogger(__name__)
 
 Base.metadata.create_all(bind=engine)
 
+# 删除过期记录
+db = SessionLocal()
+try:
+    deleted_count = Mindmap.delete_expired_records(db)
+    if deleted_count > 0:
+        logger.info(f"Deleted {deleted_count} expired mindmap records")
+finally:
+    db.close()
+
 app = FastAPI(title=settings.app_name)
 
 app.add_middleware(
diff --git a/backend/app/models.py b/backend/app/models.py
index 38828e6..5a9465d 100644
--- a/backend/app/models.py
+++ b/backend/app/models.py
@@ -1,7 +1,7 @@
-from datetime import datetime
+from datetime import datetime, timedelta
 
 from sqlalchemy import DateTime, Integer, String, Text
-from sqlalchemy.orm import Mapped, mapped_column
+from sqlalchemy.orm import Mapped, mapped_column, Session
 
 from app.database import Base
 
@@ -22,3 +22,11 @@ class Mindmap(Base):
     updated_at: Mapped[datetime] = mapped_column(
         DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False
     )
+
+    @classmethod
+    def delete_expired_records(cls, db: Session, days: int = 5) -> int:
+        """删除超过指定天数的记录"""
+        cutoff_date = datetime.utcnow() - timedelta(days=days)
+        deleted = db.query(cls).filter(cls.created_at < cutoff_date).delete()
+        db.commit()
+        return deleted
diff --git a/backend/app/routers/mindmaps.py b/backend/app/routers/mindmaps.py
index 71880c3..0071bd2 100644
--- a/backend/app/routers/mindmaps.py
+++ b/backend/app/routers/mindmaps.py
@@ -1,4 +1,5 @@
 import json
+import logging
 import secrets
 
 from fastapi import APIRouter, Depends, HTTPException, status
@@ -9,6 +10,8 @@ from app.database import get_db
 from app.models import Mindmap
 from app.schemas import MindmapCreateRequest, MindmapNode, MindmapResponse
 
+logger = logging.getLogger(__name__)
+
 router = APIRouter(prefix="/mindmaps", tags=["mindmaps"])
 
 
@@ -44,6 +47,11 @@ def create_mindmap(
     payload: MindmapCreateRequest,
     db: Session = Depends(get_db),
 ) -> MindmapResponse:
+    # 先删除过期记录
+    deleted_count = Mindmap.delete_expired_records(db)
+    if deleted_count > 0:
+        logger.info(f"Deleted {deleted_count} expired mindmap records")
+    
     title = extract_title_from_json(payload.mindmap_json)
     raw_json = json.dumps(payload.mindmap_json, ensure_ascii=False)
     unique_id = generate_unique_id()