diff --git a/backend/services/referral-service/src/api/controllers/referral.controller.ts b/backend/services/referral-service/src/api/controllers/referral.controller.ts
index 13a03a5e..3949fd9d 100644
--- a/backend/services/referral-service/src/api/controllers/referral.controller.ts
+++ b/backend/services/referral-service/src/api/controllers/referral.controller.ts
@@ -123,7 +123,7 @@ export class ReferralController {
   })
   async getReferralChainForReward(
     @Param('userId') userId: string,
-  ): Promise<{ ancestors: Array<{ userId: bigint; hasPlanted: boolean }> }> {
+  ): Promise<{ ancestors: Array<{ userId: string; hasPlanted: boolean }> }> {
     const userIdBigInt = BigInt(userId);
 
     // 获取用户的推荐关系
@@ -140,7 +140,7 @@ export class ReferralController {
     return {
       ancestors: [
         {
-          userId: referrerId,
+          userId: referrerId.toString(),
           hasPlanted,
         },
       ],