diff --git a/backend/services/accountgroup/service.go b/backend/services/accountgroup/service.go
index e9ead17..b4d9158 100644
--- a/backend/services/accountgroup/service.go
+++ b/backend/services/accountgroup/service.go
@@ -21,14 +21,15 @@ var (
 // ScopePredicate 的外层必须是用户表。使用实时子查询，不缓存管理员的分组范围。
 // 未建立成员关系的旧账号以及新账号都属于默认分组，无需迁移或复制账号数据。
 func ScopePredicate(actorID int) (string, []any) {
-	return `(id IN (
+	return `((id IN (
 		SELECT gm.user_id FROM account_group_member gm
 		JOIN account_group_member am ON gm.group_id = am.group_id
 		WHERE am.user_id = ?
 	) OR ((id NOT IN (SELECT user_id FROM account_group_member)
 		OR id IN (SELECT user_id FROM account_group_member WHERE group_id = 0))
 		AND (NOT EXISTS (SELECT 1 FROM account_group_member WHERE user_id = ?)
-		OR EXISTS (SELECT 1 FROM account_group_member WHERE user_id = ? AND group_id = 0))))`,
+		OR EXISTS (SELECT 1 FROM account_group_member WHERE user_id = ? AND group_id = 0))))
+		AND NOT ` + models.SuperAdminPredicate + `)`,
 		[]any{actorID, actorID, actorID}
 }
 
diff --git a/backend/services/accountgroup/service_test.go b/backend/services/accountgroup/service_test.go
new file mode 100644
index 0000000..a7b43bf
--- /dev/null
+++ b/backend/services/accountgroup/service_test.go
@@ -0,0 +1,43 @@
+package accountgroup
+
+import (
+	"testing"
+
+	"git.pcux.cn/xuans/Smail/models"
+	"git.pcux.cn/xuans/Smail/services/access"
+	_ "modernc.org/sqlite"
+	"xorm.io/xorm"
+)
+
+func TestCanAccessExcludesSuperAdminFromAdminScope(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.AccountGroupMember)); err != nil {
+		t.Fatal(err)
+	}
+
+	superAdmin := models.User{Account: "superadmin", Name: "超级管理员", Role: string(access.RoleSuperAdmin)}
+	admin := models.User{Account: "admin", Name: "分组管理员", Role: string(access.RoleAdmin), IsAdmin: 1}
+	member := models.User{Account: "member", Name: "普通用户", Role: string(access.RoleUser)}
+	if _, err := engine.Insert(&superAdmin, &admin, &member); err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := engine.Insert(
+		&models.AccountGroupMember{UserID: admin.ID, GroupID: 1},
+		&models.AccountGroupMember{UserID: member.ID, GroupID: 1},
+	); err != nil {
+		t.Fatal(err)
+	}
+
+	if CanAccess(engine, admin.ID, access.RoleAdmin, superAdmin.ID) {
+		t.Fatal("管理员不应访问超级管理员账户")
+	}
+	if !CanAccess(engine, admin.ID, access.RoleAdmin, member.ID) {
+		t.Fatal("管理员应访问同组普通用户账户")
+	}
+}