diff --git a/backend/controllers/account_group.go b/backend/controllers/account_group.go
index 15845fe..b901d5b 100644
--- a/backend/controllers/account_group.go
+++ b/backend/controllers/account_group.go
@@ -125,14 +125,27 @@ func SetAccountGroupMembership(ctx *context.Context, w http.ResponseWriter, req
 		writeAccountGroupError(w, accountgroup.ErrConflict)
 		return
 	}
-	if err := accountgroup.SetMembership(
-		db.Instance,
-		user,
-		input.GroupIDs,
+	guards := []accountgroup.WriteGuard{
 		accountWriteGuard(ctx, user),
 		accountgroup.MembershipScopeGuard(ctx.UserID, ctx.EffectiveRole(), input.GroupIDs),
-	); err != nil {
-		writeAccountGroupError(w, err)
+	}
+	var setErr error
+	if ctx.EffectiveRole() == access.RoleAdmin {
+		visibleGroups, visibleErr := accountgroup.VisibleGroups(db.Instance, ctx.UserID, ctx.EffectiveRole())
+		if visibleErr != nil {
+			writeAccountGroupError(w, visibleErr)
+			return
+		}
+		editableGroupIDs := make([]int, 0, len(visibleGroups))
+		for _, group := range visibleGroups {
+			editableGroupIDs = append(editableGroupIDs, group.ID)
+		}
+		setErr = accountgroup.SetScopedMembership(db.Instance, user, input.GroupIDs, editableGroupIDs, guards...)
+	} else {
+		setErr = accountgroup.SetMembership(db.Instance, user, input.GroupIDs, guards...)
+	}
+	if setErr != nil {
+		writeAccountGroupError(w, setErr)
 		return
 	}
 	InvalidateSecurityRuntimeUser(user.ID, user.Account)
diff --git a/backend/controllers/user.go b/backend/controllers/user.go
index 9f37bd9..75f5fd7 100644
--- a/backend/controllers/user.go
+++ b/backend/controllers/user.go
@@ -273,7 +273,9 @@ func UserList(ctx *context.Context, w http.ResponseWriter, req *http.Request) {
 	}
 	items := make([]userListItem, 0, len(users))
 	memberships := map[int][]int{}
-	if ctx.EffectiveRole() == access.RoleSuperAdmin {
+	groupManager := ctx.EffectiveRole() == access.RoleSuperAdmin || ctx.EffectiveRole() == access.RoleAdmin
+	visibleMemberships := map[int]struct{}{}
+	if groupManager {
 		ids := make([]int, 0, len(users))
 		for _, user := range users {
 			ids = append(ids, user.ID)
@@ -283,10 +285,30 @@ func UserList(ctx *context.Context, w http.ResponseWriter, req *http.Request) {
 			writeAccountGroupError(w, err)
 			return
 		}
+		if ctx.EffectiveRole() == access.RoleAdmin {
+			visibleGroups, visibleErr := accountgroup.VisibleGroups(db.Instance, ctx.UserID, ctx.EffectiveRole())
+			if visibleErr != nil {
+				writeAccountGroupError(w, visibleErr)
+				return
+			}
+			for _, group := range visibleGroups {
+				visibleMemberships[group.ID] = struct{}{}
+			}
+		}
 	}
 	for _, user := range users {
+		groupIDs := memberships[user.ID]
+		if ctx.EffectiveRole() == access.RoleAdmin {
+			filtered := make([]int, 0, len(groupIDs))
+			for _, groupID := range groupIDs {
+				if _, ok := visibleMemberships[groupID]; ok {
+					filtered = append(filtered, groupID)
+				}
+			}
+			groupIDs = filtered
+		}
 		items = append(items, userListItem{
-			GroupIDs:                memberships[user.ID],
+			GroupIDs:                groupIDs,
 			ID:                      user.ID,
 			Account:                 user.Account,
 			Name:                    user.Name,
@@ -298,7 +320,7 @@ func UserList(ctx *context.Context, w http.ResponseWriter, req *http.Request) {
 			ExternalEmailEnabled:    user.ExternalEmailEnabled == 1,
 			ExternalEmailConfigured: externalEmailConfigured[user.ID],
 		})
-		if ctx.EffectiveRole() == access.RoleSuperAdmin {
+		if groupManager {
 			items[len(items)-1].MembershipVersion = user.SecurityVersion
 		}
 	}
diff --git a/backend/services/accountgroup/service.go b/backend/services/accountgroup/service.go
index 2f68413..f51eced 100644
--- a/backend/services/accountgroup/service.go
+++ b/backend/services/accountgroup/service.go
@@ -296,6 +296,15 @@ func Guard(actorID int, role access.Role, sessionVersion, securityVersion int, t
 }
 
 func SetMembership(engine *xorm.Engine, user models.User, input []int, guards ...WriteGuard) error {
+	return setMembership(engine, user, input, nil, guards...)
+}
+
+// SetScopedMembership 只替换可管理分组，保留目标账号在其他分组中的成员关系。
+func SetScopedMembership(engine *xorm.Engine, user models.User, input []int, editableGroupIDs []int, guards ...WriteGuard) error {
+	return setMembership(engine, user, input, editableGroupIDs, guards...)
+}
+
+func setMembership(engine *xorm.Engine, user models.User, input []int, editableGroupIDs []int, guards ...WriteGuard) error {
 	if engine == nil || user.ID <= 0 {
 		return ErrDenied
 	}
@@ -323,6 +332,24 @@ func SetMembership(engine *xorm.Engine, user models.User, input []int, guards ..
 	if err != nil {
 		return err
 	}
+	if editableGroupIDs != nil {
+		editable := make(map[int]struct{}, len(editableGroupIDs))
+		for _, groupID := range editableGroupIDs {
+			editable[groupID] = struct{}{}
+		}
+		existing := make([]models.AccountGroupMember, 0)
+		if err := tx.Where(`user_id = ?`, user.ID).Find(&existing); err != nil {
+			return err
+		}
+		preserved := make([]int, 0, len(existing)+len(ids))
+		for _, row := range existing {
+			if _, ok := editable[row.GroupID]; !ok {
+				preserved = append(preserved, row.GroupID)
+			}
+		}
+		ids = append(preserved, ids...)
+		sort.Ints(ids)
+	}
 	if err := ReplaceMembership(tx, user.ID, ids); err != nil {
 		return err
 	}
diff --git a/backend/services/accountgroup/service_test.go b/backend/services/accountgroup/service_test.go
index 8a0cf77..91bdca5 100644
--- a/backend/services/accountgroup/service_test.go
+++ b/backend/services/accountgroup/service_test.go
@@ -135,3 +135,35 @@ func TestValidateMembershipKeepsAdminMultiGroupAndUserSingleGroupRules(t *testin
 		t.Fatalf("普通用户不应允许多个分组，得到：%v", err)
 	}
 }
+
+func TestSetScopedMembershipPreservesGroupsOutsideAdminScope(t *testing.T) {
+	engine, err := xorm.NewEngine(`sqlite`, `:memory:`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer engine.Close()
+	if err := engine.Sync2(new(models.User), new(models.AccountGroup), new(models.AccountGroupMember)); err != nil {
+		t.Fatal(err)
+	}
+	target := models.User{Account: `target`, Name: `Target`, Role: string(access.RoleUser), SessionVersion: 1, SecurityVersion: 1}
+	if _, err := engine.Insert(&target); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := engine.Insert(&models.AccountGroup{ID: 1, Name: `visible`}, &models.AccountGroup{ID: 2, Name: `hidden`}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := engine.Insert(&models.AccountGroupMember{UserID: target.ID, GroupID: 1}, &models.AccountGroupMember{UserID: target.ID, GroupID: 2}); err != nil {
+		t.Fatal(err)
+	}
+	allow := func(*xorm.Session) error { return nil }
+	if err := SetScopedMembership(engine, target, []int{0}, []int{0, 1}, allow); err != nil {
+		t.Fatal(err)
+	}
+	rows := make([]models.AccountGroupMember, 0)
+	if err := engine.Where(`user_id = ?`, target.ID).Asc(`group_id`).Find(&rows); err != nil {
+		t.Fatal(err)
+	}
+	if len(rows) != 2 || rows[0].GroupID != 0 || rows[1].GroupID != 2 {
+		t.Fatalf(`scoped membership changed an inaccessible group: %+v`, rows)
+	}
+}