diff --git a/backend/ent/runtime/runtime.go b/backend/ent/runtime/runtime.go
index da0accd7..0b254b3e 100644
--- a/backend/ent/runtime/runtime.go
+++ b/backend/ent/runtime/runtime.go
@@ -415,10 +415,6 @@ func init() {
 			return nil
 		}
 	}()
-	// settingDescValue is the schema descriptor for value field.
-	settingDescValue := settingFields[1].Descriptor()
-	// setting.ValueValidator is a validator for the "value" field. It is called by the builders before save.
-	setting.ValueValidator = settingDescValue.Validators[0].(func(string) error)
 	// settingDescUpdatedAt is the schema descriptor for updated_at field.
 	settingDescUpdatedAt := settingFields[2].Descriptor()
 	// setting.DefaultUpdatedAt holds the default value on creation for the updated_at field.
diff --git a/backend/ent/schema/setting.go b/backend/ent/schema/setting.go
index 3f896fab..0acfde59 100644
--- a/backend/ent/schema/setting.go
+++ b/backend/ent/schema/setting.go
@@ -36,7 +36,6 @@ func (Setting) Fields() []ent.Field {
 			NotEmpty().
 			Unique(),
 		field.String("value").
-			NotEmpty().
 			SchemaType(map[string]string{
 				dialect.Postgres: "text",
 			}),
diff --git a/backend/ent/setting/setting.go b/backend/ent/setting/setting.go
index feb86b87..79abe970 100644
--- a/backend/ent/setting/setting.go
+++ b/backend/ent/setting/setting.go
@@ -44,8 +44,6 @@ func ValidColumn(column string) bool {
 var (
 	// KeyValidator is a validator for the "key" field. It is called by the builders before save.
 	KeyValidator func(string) error
-	// ValueValidator is a validator for the "value" field. It is called by the builders before save.
-	ValueValidator func(string) error
 	// DefaultUpdatedAt holds the default value on creation for the "updated_at" field.
 	DefaultUpdatedAt func() time.Time
 	// UpdateDefaultUpdatedAt holds the default value on update for the "updated_at" field.
diff --git a/backend/ent/setting_create.go b/backend/ent/setting_create.go
index 66c1231e..553261e7 100644
--- a/backend/ent/setting_create.go
+++ b/backend/ent/setting_create.go
@@ -102,11 +102,6 @@ func (_c *SettingCreate) check() error {
 	if _, ok := _c.mutation.Value(); !ok {
 		return &ValidationError{Name: "value", err: errors.New(`ent: missing required field "Setting.value"`)}
 	}
-	if v, ok := _c.mutation.Value(); ok {
-		if err := setting.ValueValidator(v); err != nil {
-			return &ValidationError{Name: "value", err: fmt.Errorf(`ent: validator failed for field "Setting.value": %w`, err)}
-		}
-	}
 	if _, ok := _c.mutation.UpdatedAt(); !ok {
 		return &ValidationError{Name: "updated_at", err: errors.New(`ent: missing required field "Setting.updated_at"`)}
 	}
diff --git a/backend/ent/setting_update.go b/backend/ent/setting_update.go
index 007fa36e..42d016d6 100644
--- a/backend/ent/setting_update.go
+++ b/backend/ent/setting_update.go
@@ -110,11 +110,6 @@ func (_u *SettingUpdate) check() error {
 			return &ValidationError{Name: "key", err: fmt.Errorf(`ent: validator failed for field "Setting.key": %w`, err)}
 		}
 	}
-	if v, ok := _u.mutation.Value(); ok {
-		if err := setting.ValueValidator(v); err != nil {
-			return &ValidationError{Name: "value", err: fmt.Errorf(`ent: validator failed for field "Setting.value": %w`, err)}
-		}
-	}
 	return nil
 }
 
@@ -254,11 +249,6 @@ func (_u *SettingUpdateOne) check() error {
 			return &ValidationError{Name: "key", err: fmt.Errorf(`ent: validator failed for field "Setting.key": %w`, err)}
 		}
 	}
-	if v, ok := _u.mutation.Value(); ok {
-		if err := setting.ValueValidator(v); err != nil {
-			return &ValidationError{Name: "value", err: fmt.Errorf(`ent: validator failed for field "Setting.value": %w`, err)}
-		}
-	}
 	return nil
 }
 
diff --git a/backend/internal/repository/setting_repo_integration_test.go b/backend/internal/repository/setting_repo_integration_test.go
index 784124f4..f91c0651 100644
--- a/backend/internal/repository/setting_repo_integration_test.go
+++ b/backend/internal/repository/setting_repo_integration_test.go
@@ -105,3 +105,59 @@ func (s *SettingRepoSuite) TestSetMultiple_Upsert() {
 	s.Require().NoError(err)
 	s.Require().Equal("new_val", got2)
 }
+
+// TestSet_EmptyValue 测试保存空字符串值
+// 这是一个回归测试，确保可选设置（如站点Logo、API端点地址等）可以保存为空字符串
+func (s *SettingRepoSuite) TestSet_EmptyValue() {
+	// 测试 Set 方法保存空值
+	s.Require().NoError(s.repo.Set(s.ctx, "empty_key", ""), "Set with empty value should succeed")
+
+	got, err := s.repo.GetValue(s.ctx, "empty_key")
+	s.Require().NoError(err, "GetValue for empty value")
+	s.Require().Equal("", got, "empty value should be preserved")
+}
+
+// TestSetMultiple_WithEmptyValues 测试批量保存包含空字符串的设置
+// 模拟用户保存站点设置时部分字段为空的场景
+func (s *SettingRepoSuite) TestSetMultiple_WithEmptyValues() {
+	// 模拟保存站点设置，部分字段有值，部分字段为空
+	settings := map[string]string{
+		"site_name":     "AICodex2API",
+		"site_subtitle": "Subscription to API",
+		"site_logo":     "",           // 用户未上传Logo
+		"api_base_url":  "",           // 用户未设置API地址
+		"contact_info":  "",           // 用户未设置联系方式
+		"doc_url":       "",           // 用户未设置文档链接
+	}
+
+	s.Require().NoError(s.repo.SetMultiple(s.ctx, settings), "SetMultiple with empty values should succeed")
+
+	// 验证所有值都正确保存
+	result, err := s.repo.GetMultiple(s.ctx, []string{"site_name", "site_subtitle", "site_logo", "api_base_url", "contact_info", "doc_url"})
+	s.Require().NoError(err, "GetMultiple after SetMultiple with empty values")
+
+	s.Require().Equal("AICodex2API", result["site_name"])
+	s.Require().Equal("Subscription to API", result["site_subtitle"])
+	s.Require().Equal("", result["site_logo"], "empty site_logo should be preserved")
+	s.Require().Equal("", result["api_base_url"], "empty api_base_url should be preserved")
+	s.Require().Equal("", result["contact_info"], "empty contact_info should be preserved")
+	s.Require().Equal("", result["doc_url"], "empty doc_url should be preserved")
+}
+
+// TestSetMultiple_UpdateToEmpty 测试将已有值更新为空字符串
+// 确保用户可以清空之前设置的值
+func (s *SettingRepoSuite) TestSetMultiple_UpdateToEmpty() {
+	// 先设置非空值
+	s.Require().NoError(s.repo.Set(s.ctx, "clearable_key", "initial_value"))
+
+	got, err := s.repo.GetValue(s.ctx, "clearable_key")
+	s.Require().NoError(err)
+	s.Require().Equal("initial_value", got)
+
+	// 更新为空值
+	s.Require().NoError(s.repo.SetMultiple(s.ctx, map[string]string{"clearable_key": ""}), "Update to empty should succeed")
+
+	got, err = s.repo.GetValue(s.ctx, "clearable_key")
+	s.Require().NoError(err)
+	s.Require().Equal("", got, "value should be updated to empty string")
+}
diff --git a/backend/migrations/015_fix_settings_unique_constraint.sql b/backend/migrations/015_fix_settings_unique_constraint.sql
new file mode 100644
index 00000000..60f8fcad
--- /dev/null
+++ b/backend/migrations/015_fix_settings_unique_constraint.sql
@@ -0,0 +1,19 @@
+-- 015_fix_settings_unique_constraint.sql
+-- 修复 settings 表 key 字段缺失的唯一约束
+-- 此约束是 ON CONFLICT ("key") DO UPDATE 语句所必需的
+
+-- 检查并添加唯一约束（如果不存在）
+DO $$
+BEGIN
+    -- 检查是否已存在唯一约束
+    IF NOT EXISTS (
+        SELECT 1 FROM pg_constraint
+        WHERE conrelid = 'settings'::regclass
+        AND contype = 'u'
+        AND conname = 'settings_key_key'
+    ) THEN
+        -- 添加唯一约束
+        ALTER TABLE settings ADD CONSTRAINT settings_key_key UNIQUE (key);
+    END IF;
+END
+$$;