diff --git a/docs/注册登录对接文档.md b/docs/注册登录对接文档.md
index bb8da04..87ed98a 100644
--- a/docs/注册登录对接文档.md
+++ b/docs/注册登录对接文档.md
@@ -31,12 +31,12 @@ Content-Type: application/json
   "username": "alice01",
   "phone": "13800138000",
   "password": "Secret123",
-  "referral_code": "ABCD2345",
+  "referral_code": "123456",
   "privacy_accepted": true
 }
 ```
 
-`referral_code` 可选；传入时必须匹配当前租户下正常会员的 `invite_code`。
+`referral_code` 必填，必须是 6 位数字，且匹配当前租户下正常会员的 `invite_code`。邀请链接可通过 `inviteCode`、`invite_code` 或 `referral_code` 参数预填注册表单。
 
 ## 4 登录
 
@@ -64,7 +64,7 @@ Content-Type: application/json
     "member_no": "MABCDEFGHIJKLMNOPQRST",
     "username": "alice01",
     "phone": "13800138000",
-    "invite_code": "EFGH6789",
+    "invite_code": "654321",
     "token": "...",
     "token_type": "Bearer",
     "expires_at": "2026-10-23T10:00:00Z"
@@ -92,7 +92,7 @@ Authorization: Bearer <token>
 | `USERNAME_INVALID_FORMAT` | 400 | 账户名格式错误 |
 | `PHONE_INVALID_FORMAT` | 400 | 手机号格式错误 |
 | `PASSWORD_INVALID_FORMAT` | 400 | 密码格式错误 |
-| `REFERRAL_CODE_INVALID` | 400 | 推荐码无效 |
+| `REFERRAL_CODE_INVALID` | 400 | 邀请码为空、格式错误或不存在 |
 | `PRIVACY_POLICY_NOT_ACCEPTED` | 400 | 未同意隐私政策 |
 | `ACCOUNT_ALREADY_REGISTERED` | 409 | 账户名或手机号已注册 |
 | `INVALID_CREDENTIALS` | 401 | 手机号或密码错误 |
diff --git a/docs/移动端任务与账户平台前后端对接文档.md b/docs/移动端任务与账户平台前后端对接文档.md
index c8c191e..e5e6778 100644
--- a/docs/移动端任务与账户平台前后端对接文档.md
+++ b/docs/移动端任务与账户平台前后端对接文档.md
@@ -167,7 +167,7 @@ Content-Type: application/json
   "username": "alice01",
   "phone": "13800138000",
   "password": "Secret123",
-  "referral_code": "ABCD2345",
+  "referral_code": "123456",
   "privacy_accepted": true
 }
 ```
@@ -177,7 +177,7 @@ Content-Type: application/json
 | `username` | string | 是 | 1–10 位小写字母或数字；后端去空格并转小写 |
 | `phone` | string | 是 | 中国大陆 11 位手机号，不带 `+86` |
 | `password` | string | 是 | 6–72 字节，不做 MD5 |
-| `referral_code` | string | 否 | 1–32 位字母或数字，必须匹配正常会员邀请码 |
+| `referral_code` | string | 是 | 6 位数字，必须匹配正常会员邀请码 |
 | `privacy_accepted` | boolean | 是 | 必须为 `true` |
 
 注册事务同时写入：
@@ -196,7 +196,7 @@ Content-Type: application/json
     "member_no": "MABCDEFGHIJKLMNOPQRST",
     "username": "alice01",
     "phone": "13800138000",
-    "invite_code": "EFGH6789",
+    "invite_code": "654321",
     "token": "random-base64url-token",
     "token_type": "Bearer",
     "expires_at": "2026-10-23T10:00:00Z"
@@ -241,7 +241,7 @@ Authorization: Bearer <token>
 | 400 | `USERNAME_INVALID_FORMAT` | 账户名格式错误 |
 | 400 | `PHONE_INVALID_FORMAT` | 手机号格式错误 |
 | 400 | `PASSWORD_INVALID_FORMAT` | 密码格式错误 |
-| 400 | `REFERRAL_CODE_INVALID` | 推荐码无效 |
+| 400 | `REFERRAL_CODE_INVALID` | 邀请码为空、格式错误或不存在 |
 | 400 | `PRIVACY_POLICY_NOT_ACCEPTED` | 未同意隐私政策 |
 | 401 | `INVALID_CREDENTIALS` | 手机号或密码错误 |
 | 409 | `ACCOUNT_ALREADY_REGISTERED` | 账户名、手机号或其他唯一字段冲突 |
@@ -265,7 +265,7 @@ GET /v1/me
     "username": "alice01",
     "phone": "13800138000",
     "avatar_url": "",
-    "invite_code": "EFGH6789",
+    "invite_code": "654321",
     "level": {
       "id": 1,
       "code": "normal",
diff --git a/internal/accounts/service.go b/internal/accounts/service.go
index e911343..5bee648 100644
--- a/internal/accounts/service.go
+++ b/internal/accounts/service.go
@@ -8,6 +8,8 @@ import (
 	"encoding/hex"
 	"encoding/json"
 	"errors"
+	"fmt"
+	"math/big"
 	"regexp"
 	"strconv"
 	"strings"
@@ -39,7 +41,7 @@ var (
 
 var (
 	phonePattern         = regexp.MustCompile(`^1[3-9][0-9]{9}$`)
-	referralPattern      = regexp.MustCompile(`^[A-Za-z0-9]{1,32}$`)
+	referralPattern      = regexp.MustCompile(`^[0-9]{6}$`)
 	tradePasswordPattern = regexp.MustCompile(`^[0-9]{6}$`)
 )
 
@@ -170,26 +172,40 @@ func (s *Service) Register(ctx context.Context, input RegisterInput) (*Result, e
 	if err != nil {
 		return nil, err
 	}
-	inviteCode, err := newPublicID("", 8)
-	if err != nil {
-		return nil, err
-	}
-	account, err := s.repository.RegisterAccount(ctx, store.AccountRegistration{
-		TenantID:     s.cfg.DefaultTenantID,
-		MemberNo:     memberNo,
-		Username:     input.Username,
-		Mobile:       input.Phone,
-		PasswordHash: string(passwordHash),
-		ReferralCode: input.ReferralCode,
-		InviteCode:   inviteCode,
-	})
-	if err != nil {
+	for attempt := 0; attempt < 10; attempt++ {
+		inviteCode, err := newInviteCode()
+		if err != nil {
+			return nil, err
+		}
+		account, err := s.repository.RegisterAccount(ctx, store.AccountRegistration{
+			TenantID:     s.cfg.DefaultTenantID,
+			MemberNo:     memberNo,
+			Username:     input.Username,
+			Mobile:       input.Phone,
+			PasswordHash: string(passwordHash),
+			ReferralCode: input.ReferralCode,
+			InviteCode:   inviteCode,
+		})
+		if errors.Is(err, store.ErrInviteCodeExists) {
+			continue
+		}
 		if errors.Is(err, store.ErrReferralInvalid) {
 			return nil, ErrReferralInvalid
 		}
-		return nil, err
+		if err != nil {
+			return nil, err
+		}
+		return s.issueSession(ctx, account, input.DeviceID)
 	}
-	return s.issueSession(ctx, account, input.DeviceID)
+	return nil, ErrUnavailable
+}
+
+func newInviteCode() (string, error) {
+	number, err := rand.Int(rand.Reader, big.NewInt(1000000))
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%06d", number.Int64()), nil
 }
 
 func validMemberName(value string) bool {
diff --git a/internal/accounts/service_test.go b/internal/accounts/service_test.go
index 398a665..3ba0674 100644
--- a/internal/accounts/service_test.go
+++ b/internal/accounts/service_test.go
@@ -48,7 +48,8 @@ func TestRegisterValidation(t *testing.T) {
 		{name: "password", input: RegisterInput{Username: "alice", Phone: "13800138000", Password: "123", PrivacyAccepted: true}, want: ErrPasswordInvalid},
 		{name: "referral required", input: RegisterInput{Username: "alice", Phone: "13800138000", Password: "secret1", PrivacyAccepted: true}, want: ErrReferralInvalid},
 		{name: "referral", input: RegisterInput{Username: "alice", Phone: "13800138000", Password: "secret1", ReferralCode: "bad!", PrivacyAccepted: true}, want: ErrReferralInvalid},
-		{name: "privacy", input: RegisterInput{Username: "alice", Phone: "13800138000", Password: "secret1", ReferralCode: "ABC123"}, want: ErrPrivacyNotAccepted},
+		{name: "referral length", input: RegisterInput{Username: "alice", Phone: "13800138000", Password: "secret1", ReferralCode: "12345", PrivacyAccepted: true}, want: ErrReferralInvalid},
+		{name: "privacy", input: RegisterInput{Username: "alice", Phone: "13800138000", Password: "secret1", ReferralCode: "123456"}, want: ErrPrivacyNotAccepted},
 	}
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
@@ -60,6 +61,15 @@ func TestRegisterValidation(t *testing.T) {
 	}
 }
 
+func TestNewInviteCodeIsSixDigits(t *testing.T) {
+	for i := 0; i < 100; i++ {
+		code, err := newInviteCode()
+		if err != nil || !referralPattern.MatchString(code) {
+			t.Fatalf("newInviteCode() = %q, %v", code, err)
+		}
+	}
+}
+
 func TestValidMemberNameSupportsChinese(t *testing.T) {
 	for _, name := range []string{"杨情", "欧阳娜娜", "Alicia", "阿依古丽·买买提"} {
 		if !validMemberName(name) {
diff --git a/internal/store/accounts.go b/internal/store/accounts.go
index 364808c..09bbead 100644
--- a/internal/store/accounts.go
+++ b/internal/store/accounts.go
@@ -67,6 +67,9 @@ func (s *Store) RegisterAccount(ctx context.Context, input AccountRegistration)
 		levelID, parentID, teamLevel, tree, input.InviteCode)
 	if err != nil {
 		if isDuplicate(err) {
+			if strings.Contains(err.Error(), "uk_app_member_invite_code") {
+				return nil, ErrInviteCodeExists
+			}
 			return nil, ErrAccountExists
 		}
 		return nil, err
diff --git a/internal/store/errors.go b/internal/store/errors.go
index b9a3703..4c484cc 100644
--- a/internal/store/errors.go
+++ b/internal/store/errors.go
@@ -4,6 +4,7 @@ import "errors"
 
 var (
 	ErrAccountExists         = errors.New("account already exists")
+	ErrInviteCodeExists      = errors.New("invite code already exists")
 	ErrAccountNotFound       = errors.New("account not found")
 	ErrAccountRestricted     = errors.New("account restricted")
 	ErrAttachmentInvalid     = errors.New("attachment invalid")
diff --git a/web/src/mobile/views/AuthView.vue b/web/src/mobile/views/AuthView.vue
index ea355dd..e37f31b 100644
--- a/web/src/mobile/views/AuthView.vue
+++ b/web/src/mobile/views/AuthView.vue
@@ -47,7 +47,8 @@
           <n-icon :component="MailOpenOutline" />
           <input
             v-model.trim="form.referral_code"
-            maxlength="32"
+            maxlength="6"
+            inputmode="numeric"
             autocomplete="off"
             placeholder="请输入邀请码（必填）"
           />
@@ -134,8 +135,8 @@
     if (mode.value === 'register' && !/^[\p{L}\p{M}·]{1,10}$/u.test(form.username)) {
       return void (error.value = '名字须为 1 至 10 个字符，支持汉字');
     }
-    if (mode.value === 'register' && !/^[A-Za-z0-9]{1,32}$/.test(form.referral_code)) {
-      return void (error.value = '请输入有效的邀请码');
+    if (mode.value === 'register' && !/^\d{6}$/.test(form.referral_code)) {
+      return void (error.value = '请输入 6 位数字邀请码');
     }
     submitting.value = true;
     try {