diff --git a/backend/app/services/snmp_service.py b/backend/app/services/snmp_service.py
index bfe24f8..ba12566 100644
--- a/backend/app/services/snmp_service.py
+++ b/backend/app/services/snmp_service.py
@@ -258,16 +258,18 @@ class SNMPService:
 
             db.commit()
 
-            # 更新 IP 资产台账中的 MAC 地址
+            # 更新 IP 资产台账中的 MAC 地址和厂商信息
             for entry in arp_entries:
                 from app.models.network import IPAddress as IPAddressModel
                 ip_addr = db.query(IPAddressModel).filter(
                     IPAddressModel.ip_address == entry['ip_address']
                 ).first()
-                if ip_addr and not ip_addr.mac_address:
-                    ip_addr.mac_address = entry['mac_address']
-                    # 识别厂商
-                    ip_addr.vendor = EnhancedScanService.get_mac_vendor(entry['mac_address'])
+                if ip_addr:
+                    if not ip_addr.mac_address:
+                        ip_addr.mac_address = entry['mac_address']
+                    # 始终尝试补全厂商（有 MAC 但没厂商时也需要）
+                    if not ip_addr.vendor and ip_addr.mac_address:
+                        ip_addr.vendor = EnhancedScanService.get_mac_vendor(ip_addr.mac_address)
 
             db.commit()
             device.last_successful_poll = now