diff --git a/jituan/services/wechat_pay.py b/jituan/services/wechat_pay.py
index b7c9780..20b1e13 100644
--- a/jituan/services/wechat_pay.py
+++ b/jituan/services/wechat_pay.py
@@ -10,6 +10,10 @@ from jituan.services.club_resolver import get_club_miniapp_appid
 
 logger = logging.getLogger(__name__)
 
+# 临时写死：微信商户 API 证书序列号（与 apiclient_key.pem 对应）
+# 后台 club 表 / settings 配置正确后可删除此覆盖
+WX_V3_CERT_SERIAL_NO_OVERRIDE = '481784CF56E872D9D8122BAC64E6BC7390803582'
+
 
 def _xml_text(root, tag, default=''):
     node = root.find(tag)
@@ -200,6 +204,11 @@ def club_id_from_order(order_id):
     return CLUB_ID_DEFAULT
 
 
+def _apply_v3_cert_serial_override(cfg):
+    cfg['CERT_SERIAL_NO'] = WX_V3_CERT_SERIAL_NO_OVERRIDE
+    return cfg
+
+
 def get_wechat_v3_config(club_id=None):
     """
     微信 V3（转账/查单）配置。
@@ -222,10 +231,10 @@ def get_wechat_v3_config(club_id=None):
         club = Club.query.get(club_id=cid)
     except Club.DoesNotExist:
         logger.warning('club %s 不存在，回落全局 V3 支付配置', cid)
-        return fallback
+        return _apply_v3_cert_serial_override(fallback)
 
     cfg_json = club.config_json or {}
-    return {
+    return _apply_v3_cert_serial_override({
         'APPID': get_club_miniapp_appid(club) or (
             fallback['APPID'] if cid == CLUB_ID_DEFAULT else ''
         ),
@@ -256,7 +265,7 @@ def get_wechat_v3_config(club_id=None):
             or fallback['TRANSFER_SCENE_ID']
         ),
         'club_id': cid,
-    }
+    })
 
 
 def club_id_for_tixian_yonghuid(yonghuid):