diff --git a/libs/rating.js b/libs/rating.js
new file mode 100644
index 0000000..cc7e95b
--- /dev/null
+++ b/libs/rating.js
@@ -0,0 +1,77 @@
+// Code by Dicint
+
+const util = require('util');
+const _ = require('lodash');
+
+function getEloWinProbability(ra, rb) {
+    return 1.0 / (1 + Math.pow(10, (rb - ra) / 400.0));
+}
+
+// 传入具体某个人的情况
+function getContestantSeed(contestantIndex, allContestants) {
+    let seed = 1;
+    let rating = allContestants[contestantIndex].currentRating;
+    for (let i = 0; i < allContestants.length; i++) {
+        if (contestantIndex != i) {
+            seed += getEloWinProbability(allContestants[i].currentRating, rating);
+        }
+    }
+    return seed;
+}
+
+function getRatingSeed(rating, allContestants) {
+    return 1 + _.sum(allContestants.map(c => getEloWinProbability(c.currentRating, rating)));
+}
+
+function getAverageRank(contestant, allContestants) {
+    const realRank = allContestants[contestant].rank;
+    const expectedRank = getContestantSeed(contestant, allContestants);
+    const average = Math.sqrt(realRank * expectedRank);
+
+    return average;
+}
+
+function getRatingToRank(contestantIndex, allContestants) {
+    let averageRank = getAverageRank(contestantIndex, allContestants);
+
+    let left = 1;// contestant.getPrevRating() - 2 * minDelta;
+    let right = 8000;// contestant.getPrevRating() + 2 * maxDelta;
+
+    while (right - left > 1) {
+        const mid = (left + right) / 2;
+        const seed = getRatingSeed(mid, allContestants);
+        if (seed < averageRank) {
+            right = mid;
+        } else {
+            left = mid;
+        }
+    }
+    return left;
+}
+
+function calculateDeltas(allContestants) {
+    let deltas = [];
+    const numberOfContestants = allContestants.length;
+    for (let i = 0; i < allContestants.length; i++) {
+        const expR = getRatingToRank(i, allContestants);
+        deltas[i] = ((expR - allContestants[i].currentRating) / 2);
+    }
+
+    // Total sum should not be more than zero.
+    const deltaSum = _.sum(deltas);
+    const inc = -deltaSum / numberOfContestants - 1;
+    deltas = deltas.map(d => d + inc);
+
+    // Sum of top-4*sqrt should be adjusted to zero.
+    const zeroSumCount = Math.min(Math.trunc(4 * Math.round(Math.sqrt(numberOfContestants))), numberOfContestants);
+    const deltaSum2 = _.sum(deltas.slice(0, zeroSumCount));
+    const inc2 = Math.min(Math.max(-deltaSum2 / zeroSumCount, -10), 0);
+    deltas = deltas.map(d => d + inc2);
+
+    return deltas;
+}
+
+module.exports = function(allContestants) {
+    const deltas = calculateDeltas(allContestants);
+    return allContestants.map((contestant, i) => ({ user: contestant.user, currentRating: contestant.currentRating + deltas[i] }));
+}
\ No newline at end of file
diff --git a/modules/admin.js b/modules/admin.js
index e448c32..92fdd69 100644
--- a/modules/admin.js
+++ b/modules/admin.js
@@ -23,6 +23,10 @@ let Article = syzoj.model('article');
 let Contest = syzoj.model('contest');
 let User = syzoj.model('user');
 let UserPrivilege = syzoj.model('user_privilege');
+const RatingCalculation = syzoj.model('rating_calculation');
+const RatingHistory = syzoj.model('rating_history');
+let ContestPlayer = syzoj.model('contest_player');
+const calcRating = require('../libs/rating');
 
 let db = syzoj.db;
 
@@ -198,6 +202,86 @@ app.post('/admin/privilege', async (req, res) => {
   }
 });
 
+app.get('/admin/rating', async (req, res) => {
+  try {
+    if (!res.locals.user || !res.locals.user.is_admin) throw new ErrorMessage('您没有权限进行此操作。');
+    const contests = await Contest.query(null, {}, [['start_time', 'desc']]);
+    const calcs = await RatingCalculation.query(null, {}, [['id', 'desc']]);
+    const util = require('util');
+    for (const calc of calcs) await calc.loadRelationships();
+
+    res.render('admin_rating', {
+      contests: contests,
+      calcs: calcs
+    });
+  } catch (e) {
+    syzoj.log(e);
+    res.render('error', {
+      err: e
+    })
+  }
+});
+
+app.post('/admin/rating/add', async (req, res) => {
+  try {
+    if (!res.locals.user || !res.locals.user.is_admin) throw new ErrorMessage('您没有权限进行此操作。');
+    const contest = await Contest.fromID(req.body.contest);
+    if (!contest) throw new ErrorMessage('无此比赛');
+
+    await contest.loadRelationships();
+    const newcalc = await RatingCalculation.create(contest.id);
+    await newcalc.save();
+
+    if (!contest.ranklist || contest.ranklist.ranklist.player_num <= 1) {
+      throw new ErrorMessage("比赛人数太少。");
+    }
+
+    const players = [];
+    for (let i = 1; i <= contest.ranklist.ranklist.player_num; i++) {
+      const user = await User.fromID((await ContestPlayer.fromID(contest.ranklist.ranklist[i])).user_id);
+      players.push({
+        user: user,
+        rank: i,
+        currentRating: user.rating
+      });
+    }
+    const newRating = calcRating(players);
+    for (let i = 0; i < newRating.length; i++) {
+      const user = newRating[i].user;
+      user.rating = newRating[i].currentRating;
+      await user.save();
+      const newHistory = await RatingHistory.create(newcalc.id, user.id, user.rating);
+      await newHistory.save();
+    }
+
+    res.redirect(syzoj.utils.makeUrl(['admin', 'rating']));
+  } catch (e) {
+    syzoj.log(e);
+    res.render('error', {
+      err: e
+    });
+  }
+});
+
+app.post('/admin/rating/delete', async (req, res) => {
+  try {
+    if (!res.locals.user || !res.locals.user.is_admin) throw new ErrorMessage('您没有权限进行此操作。');
+    const calcList = await RatingCalculation.query(null, { id: { $gte: req.body.calc_id } }, [['id', 'desc']]);
+    if (calcList.length === 0) throw new ErrorMessage('ID 不正确');
+
+    for (let i = 0; i < calcList.length; i++) {
+      await calcList[i].delete();
+    }
+
+    res.redirect(syzoj.utils.makeUrl(['admin', 'rating']));
+  } catch (e) {
+    syzoj.log(e);
+    res.render('error', {
+      err: e
+    });
+  }
+});
+
 app.get('/admin/other', async (req, res) => {
   try {
     if (!res.locals.user || !res.locals.user.is_admin) throw new ErrorMessage('您没有权限进行此操作。');
@@ -233,7 +317,7 @@ app.post('/admin/other', async (req, res) => {
 
     if (req.body.type === 'reset_count') {
       const problems = await Problem.query();
-      for(const p of problems) {
+      for (const p of problems) {
         await p.resetSubmissionCount();
       }
     } else {
@@ -248,7 +332,6 @@ app.post('/admin/other', async (req, res) => {
     })
   }
 });
-
 app.post('/admin/rejudge', async (req, res) => {
   try {
     if (!res.locals.user || !res.locals.user.is_admin) throw new ErrorMessage('您没有权限进行此操作。');
diff --git a/views/admin_header.ejs b/views/admin_header.ejs
index 23bcad1..b78fae7 100644
--- a/views/admin_header.ejs
+++ b/views/admin_header.ejs
@@ -5,6 +5,7 @@ let items = {
   privilege: '权限管理',
   rejudge: '一键重测',
   links: '友链管理',
+  rating: 'Rating 管理',
   raw: '配置文件',
   other: '其他操作'
 };
diff --git a/views/admin_rating.ejs b/views/admin_rating.ejs
new file mode 100644
index 0000000..b50d0e9
--- /dev/null
+++ b/views/admin_rating.ejs
@@ -0,0 +1,34 @@
+<% this.adminPage = 'rating'; %>
+<% include admin_header %>
+<form action="<%= syzoj.utils.makeUrl(['admin', 'rating', 'add']) %>" method="post" class="ui form">
+  <div class="field">
+    <label>比赛</label>
+    <div class="ui fluid search selection dropdown">
+      <input type="hidden" name="contest">
+      <i class="dropdown icon"></i>
+      <div class="default text">选择比赛</div>
+      <div class="menu">
+        <% for (const contest of contests) { %>
+          <div class="item" data-value="<%= contest.id %>"><%= contest.title %></div>
+        <% } %>
+      </div>
+    </div>
+  </div>
+  <button class="ui blue button" name="type" value="doit" type="submit">计算此比赛的 Rating</button>
+</form>
+
+注意：如果删除一个比赛的 Rating，则该比赛之上的所有比赛也将被删除，Rating 将还原至该比赛之前的状态！
+<form class="have-csrf" action="<%= syzoj.utils.makeUrl(['admin', 'rating', 'delete']) %>" method="POST">
+  <input type="hidden" name="_csrf" value="<%= req.csrfToken() %>" />
+  <div class="ui relaxed divided list">
+    <% for (const calc of calcs) { %>
+      <div class="item">
+        <%= calc.contest.title %>
+        <button name="calc_id" value="<%= calc.id %>" type="submit" style="color: #000; padding: 0; border: none; background: none;"><i class="remove icon"></i></button>
+      </div>
+    <% } %>
+  </div>
+</div>
+</form>
+<% include admin_footer %>
+<script>$('.selection.dropdown').dropdown();</script>
\ No newline at end of file