diff --git a/backend/app/api/v1/enhanced_scan.py b/backend/app/api/v1/enhanced_scan.py
index 59307f2..9e2d190 100644
--- a/backend/app/api/v1/enhanced_scan.py
+++ b/backend/app/api/v1/enhanced_scan.py
@@ -113,7 +113,8 @@ def comprehensive_scan_ip(
     EnhancedScanService.update_ip_from_scan_result(db, result)
 
     # 刷新所属网段统计字段（used_ips/reserved_ips），保证网段列表利用率能即时反映
-    db_ip = db.query(IPAddress).filter(IPAddress.ip_address == ip_address).first()
+    from app.models.network import IPAddress as IPAddressModel
+    db_ip = db.query(IPAddressModel).filter(IPAddressModel.ip_address == ip_address).first()
     if db_ip:
         NetworkService.get_stats(db, db_ip.network_id)
 
diff --git a/backend/app/services/enhanced_scan_service.py b/backend/app/services/enhanced_scan_service.py
index ee5ef99..27b04bc 100644
--- a/backend/app/services/enhanced_scan_service.py
+++ b/backend/app/services/enhanced_scan_service.py
@@ -429,17 +429,7 @@ class EnhancedScanService:
 
         # 如果IP不存在，尝试自动创建
         if not db_ip:
-            network = db.query(Network).filter(
-                Network.cidr.op('@>')((ip_address + '/32').encode('utf-8'))
-            ).first()
-            if not network:
-                for net in db.query(Network).all():
-                    try:
-                        if ip_address in ipaddress.ip_network(net.cidr, strict=False):
-                            network = net
-                            break
-                    except Exception:
-                        pass
+            network = EnhancedScanService._find_network_for_ip(db, ip_address)
             if not network:
                 logger.warning(f"无法为扫描到的IP {ip_address} 找到所属网段，跳过创建")
                 return
@@ -481,6 +471,31 @@ class EnhancedScanService:
 
         return db_ip
 
+    @staticmethod
+    def _find_network_for_ip(db: Session, ip_address: str) -> Optional[Network]:
+        """
+        查找 IP 所属的网段（兼容 MySQL，不使用 PostgreSQL 的 @> 操作符）。
+        优先按网段越大越精确匹配，无法精确匹配时返回包含该 IP 的最小/最合适网段。
+        """
+        try:
+            target = ipaddress.ip_address(ip_address)
+        except ValueError:
+            return None
+        best = None
+        best_prefix = -1
+        for net in db.query(Network).all():
+            try:
+                cidr = str(net.cidr)
+                net_obj = ipaddress.ip_network(cidr, strict=False)
+                if target in net_obj:
+                    # 取前缀最长的（网段最小、最精确）
+                    if net_obj.prefixlen > best_prefix:
+                        best = net
+                        best_prefix = net_obj.prefixlen
+            except Exception:
+                continue
+        return best
+
     @staticmethod
     def bulk_update_ips_from_scan(db: Session, scan_results: List[Dict[str, Any]]):
         """批量更新IP信息"""