diff --git a/backend/services/identity-service/src/api/dto/request/register-by-phone.dto.ts b/backend/services/identity-service/src/api/dto/request/register-by-phone.dto.ts
index 1b149b3d..c1e57220 100644
--- a/backend/services/identity-service/src/api/dto/request/register-by-phone.dto.ts
+++ b/backend/services/identity-service/src/api/dto/request/register-by-phone.dto.ts
@@ -54,12 +54,12 @@ export class RegisterByPhoneDto {
   @IsObject()
   deviceName?: DeviceNameDto;
 
-  @ApiPropertyOptional({
-    example: 'RWAABC1234',
-    description: '邀请人推荐码 (6-20位大写字母和数字)',
+  @ApiProperty({
+    example: 'SEED01',
+    description: '邀请人推荐码 (6-20位大写字母和数字) - 必填',
   })
-  @IsOptional()
   @IsString()
+  @IsNotEmpty({ message: '推荐码不能为空' })
   @Matches(/^[A-Z0-9]{6,20}$/, { message: '推荐码格式错误' })
-  inviterReferralCode?: string;
+  inviterReferralCode: string;
 }
diff --git a/backend/services/identity-service/src/application/services/user-application.service.ts b/backend/services/identity-service/src/application/services/user-application.service.ts
index 71f24baf..f4c393a8 100644
--- a/backend/services/identity-service/src/application/services/user-application.service.ts
+++ b/backend/services/identity-service/src/application/services/user-application.service.ts
@@ -248,26 +248,31 @@ export class UserApplicationService {
     }
     this.logger.log(`[REGISTER] Phone number validated`);
 
-    // 3. 验证邀请码
-    let inviterSequence: AccountSequence | null = null;
-    if (command.inviterReferralCode) {
-      const referralCode = ReferralCode.create(command.inviterReferralCode);
-      const referralValidation =
-        await this.validatorService.validateReferralCode(referralCode);
-      if (!referralValidation.isValid) {
-        this.logger.warn(
-          `[REGISTER] Referral code invalid: ${command.inviterReferralCode}`,
-        );
-        throw new ApplicationError(referralValidation.errorMessage!);
-      }
-      const inviter =
-        await this.userRepository.findByReferralCode(referralCode);
-      inviterSequence = inviter!.accountSequence;
-      this.logger.log(
-        `[REGISTER] Inviter validated: ${inviterSequence.value}`,
-      );
+    // 3. 验证邀请码 (必填)
+    if (!command.inviterReferralCode) {
+      this.logger.warn(`[REGISTER] Missing required referral code`);
+      throw new ApplicationError('推荐码不能为空');
     }
 
+    const referralCode = ReferralCode.create(command.inviterReferralCode);
+    const referralValidation =
+      await this.validatorService.validateReferralCode(referralCode);
+    if (!referralValidation.isValid) {
+      this.logger.warn(
+        `[REGISTER] Referral code invalid: ${command.inviterReferralCode}`,
+      );
+      throw new ApplicationError(referralValidation.errorMessage!);
+    }
+    const inviter = await this.userRepository.findByReferralCode(referralCode);
+    if (!inviter) {
+      this.logger.warn(
+        `[REGISTER] Inviter not found for code: ${command.inviterReferralCode}`,
+      );
+      throw new ApplicationError('推荐码对应的用户不存在');
+    }
+    const inviterSequence = inviter.accountSequence;
+    this.logger.log(`[REGISTER] Inviter validated: ${inviterSequence.value}`);
+
     // 4. 生成用户序列号
     const accountSequence =
       await this.sequenceGenerator.generateNextUserSequence();
diff --git a/backend/services/referral-service/prisma/seed.ts b/backend/services/referral-service/prisma/seed.ts
index b4204ced..e9c80c8b 100644
--- a/backend/services/referral-service/prisma/seed.ts
+++ b/backend/services/referral-service/prisma/seed.ts
@@ -7,8 +7,8 @@ const prisma = new PrismaClient();
 // 用于为未来的注册用户提供初始推荐码
 // ============================================
 const SEED_USER = {
-  userId: BigInt(5),
-  accountSequence: 'D25122100000',  // 种子用户 (序号0，真实用户从1开始)
+  userId: BigInt(25129999999),  // 从 accountSequence 去掉 D 前缀
+  accountSequence: 'D25129999999',  // 种子用户 (特殊序号，区别于真实用户)
   myReferralCode: 'SEED01',
   usedReferralCode: null,  // 根节点无推荐人
   referrerId: null,        // 根节点