diff --git a/backend/internal/auth/jwt.go b/backend/internal/auth/jwt.go
index 1da1ac0..01121ff 100644
--- a/backend/internal/auth/jwt.go
+++ b/backend/internal/auth/jwt.go
@@ -15,10 +15,17 @@ var (
 	ErrInvalidToken = errors.New("invalid or expired token")
 )
 
+// 令牌类型常量。
+const (
+	TokenTypeAccess  = "access"
+	TokenTypeRefresh = "refresh"
+)
+
 // Claims JWT 声明。
 type Claims struct {
-	UserID   string `json:"user_id"`
-	Username string `json:"username"`
+	UserID    string `json:"user_id"`
+	Username  string `json:"username"`
+	TokenType string `json:"token_type"`
 	jwt.RegisteredClaims
 }
 
@@ -45,8 +52,9 @@ func (tm *TokenManager) GeneratePair(userID, username string) (access, refresh s
 
 	// access token
 	accessClaims := &Claims{
-		UserID:   userID,
-		Username: username,
+		UserID:    userID,
+		Username:  username,
+		TokenType: TokenTypeAccess,
 		RegisteredClaims: jwt.RegisteredClaims{
 			ExpiresAt: jwt.NewNumericDate(now.Add(tm.accessTTL)),
 			IssuedAt:  jwt.NewNumericDate(now),
@@ -62,8 +70,9 @@ func (tm *TokenManager) GeneratePair(userID, username string) (access, refresh s
 	// refresh token（含唯一 token_id 用于 DB 关联）
 	tokenID := uuid.New().String()
 	refreshClaims := &Claims{
-		UserID:   userID,
-		Username: username,
+		UserID:    userID,
+		Username:  username,
+		TokenType: TokenTypeRefresh,
 		RegisteredClaims: jwt.RegisteredClaims{
 			ID:        tokenID,
 			ExpiresAt: jwt.NewNumericDate(now.Add(tm.refreshTTL)),
@@ -78,12 +87,26 @@ func (tm *TokenManager) GeneratePair(userID, username string) (access, refresh s
 
 // ValidateAccess 校验 access token 并返回 Claims。
 func (tm *TokenManager) ValidateAccess(tokenStr string) (*Claims, error) {
-	return tm.validate(tokenStr)
+	claims, err := tm.validate(tokenStr)
+	if err != nil {
+		return nil, err
+	}
+	if claims.TokenType != TokenTypeAccess {
+		return nil, ErrInvalidToken
+	}
+	return claims, nil
 }
 
 // ValidateRefresh 校验 refresh token 并返回 Claims。
 func (tm *TokenManager) ValidateRefresh(tokenStr string) (*Claims, error) {
-	return tm.validate(tokenStr)
+	claims, err := tm.validate(tokenStr)
+	if err != nil {
+		return nil, err
+	}
+	if claims.TokenType != TokenTypeRefresh {
+		return nil, ErrInvalidToken
+	}
+	return claims, nil
 }
 
 // validate 解析并校验 JWT。
diff --git a/backend/internal/auth/jwt_test.go b/backend/internal/auth/jwt_test.go
index 35b12fa..7178bae 100644
--- a/backend/internal/auth/jwt_test.go
+++ b/backend/internal/auth/jwt_test.go
@@ -103,6 +103,44 @@ func TestValidateRefresh_ExpiredToken(t *testing.T) {
 	assert.ErrorIs(t, err, ErrInvalidToken)
 }
 
+func TestValidateAccess_RejectsRefreshToken(t *testing.T) {
+	tm := NewTokenManager("test-secret-key", 15*time.Minute, 7*24*time.Hour)
+
+	_, refresh, err := tm.GeneratePair("user-123", "alice")
+	require.NoError(t, err)
+
+	// refresh token 不能通过 access 校验
+	_, err = tm.ValidateAccess(refresh)
+	assert.ErrorIs(t, err, ErrInvalidToken)
+}
+
+func TestValidateRefresh_RejectsAccessToken(t *testing.T) {
+	tm := NewTokenManager("test-secret-key", 15*time.Minute, 7*24*time.Hour)
+
+	access, _, err := tm.GeneratePair("user-123", "alice")
+	require.NoError(t, err)
+
+	// access token 不能通过 refresh 校验
+	_, err = tm.ValidateRefresh(access)
+	assert.ErrorIs(t, err, ErrInvalidToken)
+}
+
+func TestGeneratePair_TokenTypesAreCorrect(t *testing.T) {
+	tm := NewTokenManager("test-secret-key", 15*time.Minute, 7*24*time.Hour)
+
+	access, refresh, err := tm.GeneratePair("user-123", "alice")
+	require.NoError(t, err)
+
+	// 通过 validate（不做类型检查）验证 token_type 字段
+	accessClaims, err := tm.validate(access)
+	require.NoError(t, err)
+	assert.Equal(t, TokenTypeAccess, accessClaims.TokenType)
+
+	refreshClaims, err := tm.validate(refresh)
+	require.NoError(t, err)
+	assert.Equal(t, TokenTypeRefresh, refreshClaims.TokenType)
+}
+
 func TestGeneratePair_TokenClaimsContainCorrectExpiry(t *testing.T) {
 	accessTTL := 15 * time.Minute
 	refreshTTL := 7 * 24 * time.Hour