diff --git a/packages/codemate-plugin/plugins/tags-entity/index.ts b/packages/codemate-plugin/plugins/tags-entity/index.ts
new file mode 100644
index 0000000000..a7023513af
--- /dev/null
+++ b/packages/codemate-plugin/plugins/tags-entity/index.ts
@@ -0,0 +1,63 @@
+import { Context, Handler, ObjectId, param, PRIV, Types } from 'hydrooj';
+import TagModel from './model';
+
+class TagManageBaseHandler extends Handler {
+    async _prepare() {
+        this.checkPriv(PRIV.PRIV_EDIT_SYSTEM);
+    }
+}
+
+class TagAddHandler extends TagManageBaseHandler {
+    @param('name', Types.String)
+    @param('alias', Types.ArrayOf<Types['String']>)
+    @param('description', Types.String)
+    async post(domainId: string, _name: string, alias: string[], _description: string) {
+        const name = JSON.parse(_name);
+        const description = JSON.parse(_description);
+        const docId = await TagModel.add(domainId, name, alias, description);
+        this.response.body = { docId };
+    }
+}
+
+class TagEditHandler extends TagManageBaseHandler {
+    @param('docId', Types.ObjectId)
+    @param('name', Types.String)
+    @param('alias', Types.ArrayOf<Types['String']>)
+    @param('description', Types.String)
+    async post(domainId: string, docId: ObjectId, _name: string, alias: string[], _description: string) {
+        const name = JSON.parse(_name);
+        const description = JSON.parse(_description);
+        await TagModel.edit(domainId, docId, name, alias, description);
+        this.response.body = { docId };
+    }
+}
+
+class TagMainHandler extends Handler {
+    async get({ domainId }) {
+        const tags = await TagModel.getMulti(domainId);
+        this.response.body = { tags };
+    }
+}
+
+class TagDeleteHandler extends TagManageBaseHandler {
+    @param('docId', Types.ObjectId)
+    async get(domainId: string, docId: ObjectId) {
+        await TagModel.del(domainId, docId);
+        this.response.body = { success: true };
+    }
+}
+
+class TagGetHandler extends Handler {
+    @param('docId', Types.String)
+    async get(domainId: string, docId: ObjectId) {
+        this.response.body = { tagDoc: await TagModel.get(domainId, docId) };
+    }
+}
+
+export async function apply(ctx: Context) {
+    ctx.Route('tag_add', '/tag/add', TagAddHandler);
+    ctx.Route('tag_edit', '/tag/edit', TagEditHandler);
+    ctx.Route('tag_main', '/tag/list', TagMainHandler);
+    ctx.Route('tag_delete', '/tag/delete', TagDeleteHandler);
+    ctx.Route('tag_get', '/tag/get', TagGetHandler);
+}
diff --git a/packages/codemate-plugin/plugins/tags-entity/model.ts b/packages/codemate-plugin/plugins/tags-entity/model.ts
new file mode 100644
index 0000000000..af3fee5def
--- /dev/null
+++ b/packages/codemate-plugin/plugins/tags-entity/model.ts
@@ -0,0 +1,39 @@
+import { Document, DocumentModel, ObjectId, Projection } from 'hydrooj';
+
+type stringDict = { [p: string]: string };
+
+export interface TagDoc extends Document {
+    name: stringDict;
+    alias: string[];
+    description: stringDict;
+}
+
+export default class TagModel {
+    static async add(domainId: string, name: stringDict, alias: string[], description: stringDict): Promise<ObjectId> {
+        return await DocumentModel.add(domainId, '', 1, DocumentModel.TYPE_TAGS, null, null, null, {
+            name,
+            alias,
+            description,
+        });
+    }
+
+    static async del(domainId: string, docId: ObjectId) {
+        await DocumentModel.deleteOne(domainId, DocumentModel.TYPE_TAGS, docId);
+    }
+
+    static async edit(domainId: string, docId: ObjectId, name: stringDict, alias: string[], description: stringDict) {
+        await DocumentModel.set(domainId, DocumentModel.TYPE_TAGS, docId, {
+            name,
+            alias,
+            description,
+        });
+    }
+
+    static async get(domainId: string, docId: ObjectId) {
+        return await DocumentModel.get(domainId, DocumentModel.TYPE_TAGS, docId);
+    }
+
+    static async getMulti(domainId: string, query?: Partial<TagDoc>, projection?: Projection<TagDoc>) {
+        return DocumentModel.getMulti(domainId, DocumentModel.TYPE_TAGS, query, projection);
+    }
+}
diff --git a/packages/hydrooj/src/interface.ts b/packages/hydrooj/src/interface.ts
index a0a4b8482b..a496cf4ae1 100644
--- a/packages/hydrooj/src/interface.ts
+++ b/packages/hydrooj/src/interface.ts
@@ -101,15 +101,15 @@ export interface Udoc extends Record<string, any> {
 
 /**
  * export const enum UserRole {
-  PRIMARY_SCHOOL_STUDENT = 0, // 小学生
-  JUNIOR_MIDDLE_SCHOOL_STUDENT = 1, // 初中生
-  SENIOR_MIDDLE_SCHOOL_STUDENT = 2, // 高中生
-  ADULT = 10, // 一般成人
-  COLLEGE_STUDENT = 11, // 大学生
-  SCHOOL_TEACHER = 12, // 中小学教师
-  INSTITUTE_TEACHER = 13, // 机构教师
-  STUDENT_PARENT = 14, // 学生家长
-}
+ PRIMARY_SCHOOL_STUDENT = 0, // 小学生
+ JUNIOR_MIDDLE_SCHOOL_STUDENT = 1, // 初中生
+ SENIOR_MIDDLE_SCHOOL_STUDENT = 2, // 高中生
+ ADULT = 10, // 一般成人
+ COLLEGE_STUDENT = 11, // 大学生
+ SCHOOL_TEACHER = 12, // 中小学教师
+ INSTITUTE_TEACHER = 13, // 机构教师
+ STUDENT_PARENT = 14, // 学生家长
+ }
  */
 
 export interface VUdoc {
@@ -156,6 +156,7 @@ export interface BaseUser {
     displayName?: string;
     studentId?: string;
 }
+
 export type BaseUserDict = Record<number, BaseUser>;
 
 export interface FileInfo {
@@ -244,18 +245,21 @@ export interface PlainContentNode {
     subType: 'html' | 'markdown';
     text: string;
 }
+
 export interface TextContentNode {
     type: 'Text';
     subType: 'html' | 'markdown';
     sectionTitle: string;
     text: string;
 }
+
 export interface SampleContentNode {
     type: 'Sample';
     text: string;
     sectionTitle: string;
     payload: [string, string];
 }
+
 // TODO drop contentNode support
 export type ContentNode = PlainContentNode | TextContentNode | SampleContentNode;
 export type Content = string | ContentNode[] | Record<string, ContentNode[]>;
@@ -279,7 +283,9 @@ declare module './model/problem' {
         content: string;
         nSubmit: number;
         nAccept: number;
+        /** @deprecated */
         tag: string[];
+        tags: ObjectId[];
         data: FileInfo[];
         additional_file: FileInfo[];
         hidden?: boolean;
@@ -384,6 +390,7 @@ export interface ScoreboardNode {
     style?: string;
     hover?: string;
 }
+
 export type ScoreboardRow = ScoreboardNode[] & { raw?: any };
 
 export type PenaltyRules = Dictionary<number>;
@@ -541,6 +548,7 @@ export interface TokenDoc {
     createAt: Date;
     updateAt: Date;
     expireAt: Date;
+
     [key: string]: any;
 }
 
@@ -647,6 +655,7 @@ export interface Task {
     type: string;
     subType?: string;
     priority: number;
+
     [key: string]: any;
 }
 
@@ -655,6 +664,7 @@ export interface Schedule {
     type: string;
     subType?: string;
     executeAfter: Date;
+
     [key: string]: any;
 }
 
@@ -795,6 +805,7 @@ export interface ProblemSearchResponse {
     total: number;
     countRelation: 'eq' | 'gte';
 }
+
 export interface ProblemSearchOptions {
     limit?: number;
     skip?: number;
@@ -813,6 +824,7 @@ export interface Lib extends Record<string, any> {
 }
 
 export type UIInjectableFields = 'ProblemAdd' | 'Notification' | 'Nav' | 'UserDropdown' | 'DomainManage' | 'ControlPanel';
+
 export interface UI {
     template: Record<string, string>;
     nodes: Record<UIInjectableFields, any[]>;
diff --git a/packages/hydrooj/src/model/document.ts b/packages/hydrooj/src/model/document.ts
index 1e2362f144..00c73bdc91 100644
--- a/packages/hydrooj/src/model/document.ts
+++ b/packages/hydrooj/src/model/document.ts
@@ -1,6 +1,7 @@
 /* eslint-disable object-curly-newline */
 import assert from 'assert';
 import { bulletin, plist } from 'codemate-plugin';
+import { TagDoc } from 'codemate-plugin/plugins/tags-entity/model';
 import { Filter, FindCursor, ObjectId, OnlyFieldsOfType, PushOperator, UpdateFilter } from 'mongodb';
 import { Context } from '../context';
 import { Content, ContestClarificationDoc, DiscussionDoc, DiscussionReplyDoc, ProblemDoc, ProblemStatusDoc, Tdoc, TrainingDoc } from '../interface';
@@ -29,6 +30,7 @@ export const TYPE_TRAINING: 40 = 40;
 /** @deprecated use `TYPE_CONTEST` with rule `homework` instead. */
 export const TYPE_HOMEWORK: 60 = 60;
 export const TYPE_BULLETIN: 80 = 80;
+export const TYPE_TAGS: 90 = 90;
 
 export interface DocType {
     [TYPE_PROBLEM]: ProblemDoc;
@@ -42,6 +44,7 @@ export interface DocType {
     [TYPE_TRAINING]: TrainingDoc;
     [TYPE_SYSTEM_PLIST]: plist.ProblemList;
     [TYPE_BULLETIN]: bulletin.BulletinDoc;
+    [TYPE_TAGS]: TagDoc;
 }
 
 export interface DocStatusType {
@@ -550,4 +553,5 @@ global.Hydro.model.document = {
     TYPE_PROBLEM_SOLUTION,
     TYPE_TRAINING,
     TYPE_BULLETIN,
+    TYPE_TAGS,
 };
diff --git a/packages/hydrooj/src/model/problem.ts b/packages/hydrooj/src/model/problem.ts
index f820ddbfbe..c3b492e098 100644
--- a/packages/hydrooj/src/model/problem.ts
+++ b/packages/hydrooj/src/model/problem.ts
@@ -22,9 +22,11 @@ import storage from './storage';
 import user from './user';
 
 export interface ProblemDoc extends Document {}
+
 export type Field = keyof ProblemDoc;
 
 const logger = new Logger('problem');
+
 function sortable(source: string) {
     return source.replace(/(\d+)/g, (str) => (str.length >= 6 ? str : '0'.repeat(6 - str.length) + str));
 }
@@ -86,6 +88,7 @@ export class ProblemModel {
         nSubmit: 0,
         nAccept: 0,
         tag: [],
+        tags: [],
         data: [],
         additional_file: [],
         stats: {},
diff --git a/packages/hydrooj/src/upgrade.ts b/packages/hydrooj/src/upgrade.ts
index 4b9dea7a36..34ae178d4e 100644
--- a/packages/hydrooj/src/upgrade.ts
+++ b/packages/hydrooj/src/upgrade.ts
@@ -1,6 +1,7 @@
 /* eslint-disable @typescript-eslint/no-unused-vars */
 /* eslint-disable no-await-in-loop */
 /* eslint-disable @typescript-eslint/naming-convention */
+import TagModel from 'codemate-plugin/plugins/tags-entity/model';
 import yaml from 'js-yaml';
 import { pick } from 'lodash';
 import moment from 'moment-timezone';
@@ -226,6 +227,7 @@ const scripts: UpgradeScript[] = [
     async function _51_52() {
         const mapping: Record<string, number> = {};
         const isStringPid = (i: string) => i.toString().includes(':');
+
         async function getProblem(domainId: string, target: string) {
             if (!target.toString().includes(':')) return await problem.get(domainId, target);
             const l = `${domainId}/${target}`;
@@ -235,6 +237,7 @@ const scripts: UpgradeScript[] = [
             mapping[l] = docId;
             return await problem.get(domainId, docId);
         }
+
         const cursor = db.collection('document').find({ docType: document.TYPE_CONTEST });
         for await (const doc of cursor) {
             const pids = [];
@@ -297,9 +300,11 @@ const scripts: UpgradeScript[] = [
     },
     async function _54_55() {
         const bulk = db.collection('document').initializeUnorderedBulkOp();
+
         function sortable(source: string) {
             return source.replace(/(\d+)/g, (str) => (str.length >= 6 ? str : '0'.repeat(6 - str.length) + str));
         }
+
         await iterateAllProblem(['pid', '_id'], async (pdoc) => {
             bulk.find({ _id: pdoc._id }).updateOne({ $set: { sort: sortable(pdoc.pid || `P${pdoc.docId}`) } });
         });
@@ -691,6 +696,21 @@ const scripts: UpgradeScript[] = [
         }
         return true;
     },
+    async function _91_92() {
+        // iterate all tags, and add a tag document according to it.
+        const tagMap = new Map<string, ObjectId>();
+        return await iterateAllProblem(['tag'], async (pdoc) => {
+            const _tags = [];
+            for (const tag of pdoc.tag) {
+                if (!tagMap.has(tag)) {
+                    const docId = await TagModel.add(pdoc.domainId, { 'zh-cn': tag }, [], { 'zh-cn': tag });
+                    tagMap.set(tag, docId);
+                }
+                _tags.push(tagMap.get(tag));
+            }
+            await problem.edit(pdoc.domainId, pdoc.docId, { tags: _tags });
+        });
+    },
 ];
 
 export default scripts;