diff --git a/packages/core/src/lib/sign-in-experience.test.ts b/packages/core/src/lib/sign-in-experience.test.ts
index 0fc506e1d..68370de97 100644
--- a/packages/core/src/lib/sign-in-experience.test.ts
+++ b/packages/core/src/lib/sign-in-experience.test.ts
@@ -1,8 +1,12 @@
-import { BrandingStyle } from '@logto/schemas';
+import { BrandingStyle, SignInMethodState } from '@logto/schemas';
 
 import RequestError from '@/errors/RequestError';
-import { validateBranding, validateTermsOfUse } from '@/lib/sign-in-experience';
-import { mockBranding } from '@/utils/mock';
+import {
+  validateBranding,
+  validateSignInMethods,
+  validateTermsOfUse,
+} from '@/lib/sign-in-experience';
+import { mockBranding, mockSignInMethods } from '@/utils/mock';
 
 describe('validate branding', () => {
   test('should throw when the UI style contains the slogan and slogan is empty', () => {
@@ -44,3 +48,29 @@ describe('validate terms of use', () => {
     }).toMatchError(new RequestError('sign_in_experiences.empty_content_url_of_terms_of_use'));
   });
 });
+
+describe('validate sign-in methods', () => {
+  describe('There must be one and only one primary sign-in method.', () => {
+    test('should throw when there is no primary sign-in method', async () => {
+      expect(() => {
+        validateSignInMethods({
+          ...mockSignInMethods,
+          username: SignInMethodState.disabled,
+        });
+      }).toMatchError(
+        new RequestError('sign_in_experiences.not_one_and_only_one_primary_sign_in_method')
+      );
+    });
+
+    test('should throw when there are more than one primary sign-in methods', async () => {
+      expect(() => {
+        validateSignInMethods({
+          ...mockSignInMethods,
+          social: SignInMethodState.primary,
+        });
+      }).toMatchError(
+        new RequestError('sign_in_experiences.not_one_and_only_one_primary_sign_in_method')
+      );
+    });
+  });
+});
diff --git a/packages/core/src/lib/sign-in-experience.ts b/packages/core/src/lib/sign-in-experience.ts
index b45898b39..362cd7e84 100644
--- a/packages/core/src/lib/sign-in-experience.ts
+++ b/packages/core/src/lib/sign-in-experience.ts
@@ -1,4 +1,10 @@
-import { Branding, BrandingStyle, TermsOfUse } from '@logto/schemas';
+import {
+  Branding,
+  BrandingStyle,
+  SignInMethods,
+  SignInMethodState,
+  TermsOfUse,
+} from '@logto/schemas';
 
 import assertThat from '@/utils/assert-that';
 
@@ -14,3 +20,13 @@ export const validateTermsOfUse = (termsOfUse: TermsOfUse) => {
     'sign_in_experiences.empty_content_url_of_terms_of_use'
   );
 };
+
+export const validateSignInMethods = (signInMethods: SignInMethods) => {
+  const signInMethodStates = Object.values(signInMethods);
+  assertThat(
+    signInMethodStates.filter((state) => state === SignInMethodState.primary).length === 1,
+    'sign_in_experiences.not_one_and_only_one_primary_sign_in_method'
+  );
+
+  // TODO: assert others next PR
+};
diff --git a/packages/core/src/routes/sign-in-experience.test.ts b/packages/core/src/routes/sign-in-experience.test.ts
index 27d5bc329..4b677d002 100644
--- a/packages/core/src/routes/sign-in-experience.test.ts
+++ b/packages/core/src/routes/sign-in-experience.test.ts
@@ -1,7 +1,7 @@
 import { SignInExperience, CreateSignInExperience, TermsOfUse } from '@logto/schemas';
 
 import * as signInExpLib from '@/lib/sign-in-experience';
-import { mockBranding, mockSignInExperience } from '@/utils/mock';
+import { mockBranding, mockSignInExperience, mockSignInMethods } from '@/utils/mock';
 import { createRequester } from '@/utils/test-utils';
 
 import signInExperiencesRoutes from './sign-in-experience';
@@ -38,15 +38,19 @@ describe('signInExperiences routes', () => {
 
     const validateBranding = jest.spyOn(signInExpLib, 'validateBranding');
     const validateTermsOfUse = jest.spyOn(signInExpLib, 'validateTermsOfUse');
+    const validateSignInMethods = jest.spyOn(signInExpLib, 'validateSignInMethods');
 
     const response = await signInExperienceRequester.patch('/sign-in-exp').send({
       branding: mockBranding,
       termsOfUse,
+      signInMethods: mockSignInMethods,
       socialSignInConnectorIds,
     });
 
     expect(validateBranding).toHaveBeenCalledWith(mockBranding);
     expect(validateTermsOfUse).toHaveBeenCalledWith(termsOfUse);
+    expect(validateSignInMethods).toHaveBeenCalledWith(mockSignInMethods);
+    // TODO: only update socialSignInConnectorIds when social sign-in is enabled.
 
     expect(response).toMatchObject({
       status: 200,
@@ -54,6 +58,7 @@ describe('signInExperiences routes', () => {
         ...mockSignInExperience,
         branding: mockBranding,
         termsOfUse,
+        signInMethods: mockSignInMethods,
         socialSignInConnectorIds,
       },
     });
diff --git a/packages/core/src/routes/sign-in-experience.ts b/packages/core/src/routes/sign-in-experience.ts
index 85ea50df6..3c18d2038 100644
--- a/packages/core/src/routes/sign-in-experience.ts
+++ b/packages/core/src/routes/sign-in-experience.ts
@@ -1,7 +1,11 @@
 import { SignInExperiences } from '@logto/schemas';
 
 import { getEnabledSocialConnectorIds } from '@/connectors';
-import { validateBranding, validateTermsOfUse } from '@/lib/sign-in-experience';
+import {
+  validateBranding,
+  validateTermsOfUse,
+  validateSignInMethods,
+} from '@/lib/sign-in-experience';
 import koaGuard from '@/middleware/koa-guard';
 import {
   findDefaultSignInExperience,
@@ -42,7 +46,7 @@ export default function signInExperiencesRoutes<T extends AuthedRouter>(router:
       body: SignInExperiences.createGuard.omit({ id: true }).partial(),
     }),
     async (ctx, next) => {
-      const { branding, termsOfUse } = ctx.guard.body;
+      const { branding, termsOfUse, signInMethods } = ctx.guard.body;
 
       if (branding) {
         validateBranding(branding);
@@ -52,7 +56,10 @@ export default function signInExperiencesRoutes<T extends AuthedRouter>(router:
         validateTermsOfUse(termsOfUse);
       }
 
-      // TODO: validate SignInMethods
+      if (signInMethods) {
+        validateSignInMethods(signInMethods);
+      }
+
       // TODO: validate socialConnectorIds
 
       // TODO: Only update socialSignInConnectorIds when social sign-in is enabled.
diff --git a/packages/core/src/utils/mock.ts b/packages/core/src/utils/mock.ts
index a210a60af..48ee24ed0 100644
--- a/packages/core/src/utils/mock.ts
+++ b/packages/core/src/utils/mock.ts
@@ -21,6 +21,7 @@ import {
   ConnectorType,
   SignInMethodState,
   Branding,
+  SignInMethods,
 } from '@logto/schemas';
 import pick from 'lodash.pick';
 
@@ -382,4 +383,11 @@ export const mockBranding: Branding = {
   logoUrl: 'http://silverhand.png',
   slogan: 'Silverhand.',
 };
+
+export const mockSignInMethods: SignInMethods = {
+  username: SignInMethodState.primary,
+  email: SignInMethodState.disabled,
+  sms: SignInMethodState.disabled,
+  social: SignInMethodState.disabled,
+};
 /* eslint-enable max-lines */
diff --git a/packages/phrases/src/locales/en.ts b/packages/phrases/src/locales/en.ts
index 0383fb68f..179c0673e 100644
--- a/packages/phrases/src/locales/en.ts
+++ b/packages/phrases/src/locales/en.ts
@@ -347,6 +347,8 @@ const errors = {
       'Empty "Terms of use" content URL. Please add the content URL if "Terms of use" is enabled.',
     empty_slogan:
       'Empty branding slogan. Please add a branding slogan if a UI style containing the slogan is selected.',
+    not_one_and_only_one_primary_sign_in_method:
+      'There must be one and only one primary sign-in method. Please check your input.',
   },
   swagger: {
     invalid_zod_type: 'Invalid Zod type, please check route guard config.',
diff --git a/packages/phrases/src/locales/zh-cn.ts b/packages/phrases/src/locales/zh-cn.ts
index b041893d5..3d8de5093 100644
--- a/packages/phrases/src/locales/zh-cn.ts
+++ b/packages/phrases/src/locales/zh-cn.ts
@@ -344,6 +344,7 @@ const errors = {
     empty_content_url_of_terms_of_use:
       '空的《用户协议》内容链接。当启用《用户协议》时，请添加其内容链接。',
     empty_slogan: '空的标语。当使用包含标语的 UI 风格时，请添加标语。',
+    not_one_and_only_one_primary_sign_in_method: '主要的登录方式必须有且仅有一个。请检查你的输入。',
   },
   swagger: {
     invalid_zod_type: '无效的 Zod 类型，请检查路由 guard 配置。',