diff --git a/lib/box/index.ts b/lib/box/index.ts
index c09a8500ff..31a3df5e21 100644
--- a/lib/box/index.ts
+++ b/lib/box/index.ts
@@ -27,8 +27,6 @@ class Box extends EventEmitter {
   public File: any;
   public ignore: any[];
   public source: any;
-  public emit: any;
-  public ctx: any;
 
   constructor(ctx: Hexo, base: string, options?: object) {
     super();
@@ -65,13 +63,13 @@ class Box extends EventEmitter {
     class _File extends File {
       public box: Box;
 
-      render(options?: any) {
+      render(options?: object) {
         return ctx.render.render({
           path: this.source
         }, options);
       }
 
-      renderSync(options?: any) {
+      renderSync(options?: object) {
         return ctx.render.renderSync({
           path: this.source
         }, options);
diff --git a/lib/extend/renderer.ts b/lib/extend/renderer.ts
index f55f92a5ec..701c5d0031 100644
--- a/lib/extend/renderer.ts
+++ b/lib/extend/renderer.ts
@@ -24,7 +24,7 @@ export interface StoreSyncFunction {
     // callback: (err: Error, value: string) => any
   ): any;
   output?: string;
-  compile?: (local: object) => string;
+  compile?: (local: object) => any;
 }
 export interface StoreFunction {
   (
@@ -37,7 +37,7 @@ export interface StoreFunction {
     callback: (err: Error, value: string) => any
   ): void;
   output?: string;
-  compile?: (local: object) => string;
+  compile?: (local: object) => any;
   disableNunjucks?: boolean;
 }
 
diff --git a/lib/hexo/multi_config_path.ts b/lib/hexo/multi_config_path.ts
index 84194400b6..978c04fca0 100644
--- a/lib/hexo/multi_config_path.ts
+++ b/lib/hexo/multi_config_path.ts
@@ -4,7 +4,7 @@ import yml from 'js-yaml';
 import { deepMerge } from 'hexo-util';
 import type Hexo from './index';
 
-export = (ctx: Hexo) => function multiConfigPath(base: string, configPaths: string, outputDir: any) {
+export = (ctx: Hexo) => function multiConfigPath(base: string, configPaths: string, outputDir: string) {
   const { log } = ctx;
   const defaultPath = join(base, '_config.yml');
 
diff --git a/lib/hexo/post.ts b/lib/hexo/post.ts
index e820b52955..34588bf76d 100644
--- a/lib/hexo/post.ts
+++ b/lib/hexo/post.ts
@@ -186,7 +186,7 @@ class PostRenderEscape {
   }
 }
 
-const prepareFrontMatter = (data: object, jsonMode: boolean) => {
+const prepareFrontMatter = (data: any, jsonMode: boolean) => {
   for (const [key, item] of Object.entries(data)) {
     if (moment.isMoment(item)) {
       data[key] = item.utc().format('YYYY-MM-DD HH:mm:ss');
@@ -232,19 +232,24 @@ interface Data {
   source?: string;
 }
 
+interface PostData {
+  title?: string;
+  layout?: string;
+  slug?: string;
+  path?: string;
+  [prop: string]: any;
+}
+
 class Post {
   public context: Hexo;
-  public config: any;
-  public tag: any;
-  public separator: string;
 
   constructor(context: Hexo) {
     this.context = context;
   }
 
-  create(data: any, callback?: (...args: any[]) => any);
-  create(data: any, replace: boolean, callback?: (...args: any[]) => any);
-  create(data: any, replace: boolean | ((...args: any[]) => any), callback?: (...args: any[]) => any) {
+  create(data: PostData, callback?: (...args: any[]) => any);
+  create(data: PostData, replace: boolean, callback?: (...args: any[]) => any);
+  create(data: PostData, replace: boolean | ((...args: any[]) => any), callback?: (...args: any[]) => any) {
     if (!callback && typeof replace === 'function') {
       callback = replace;
       replace = false;
@@ -288,7 +293,7 @@ class Post {
     });
   }
 
-  _renderScaffold(data: any) {
+  _renderScaffold(data: PostData) {
     const { tag } = this.context.extend;
     let splitted;
 
@@ -330,7 +335,7 @@ class Post {
     });
   }
 
-  publish(data: any, replace: boolean, callback: (...args: any[]) => any) {
+  publish(data: PostData, replace: boolean, callback?: (...args: any[]) => any) {
     if (!callback && typeof replace === 'function') {
       callback = replace;
       replace = false;
@@ -383,7 +388,7 @@ class Post {
     }).thenReturn(result).asCallback(callback);
   }
 
-  render(source: string, data: Data = {}, callback: (...args: any[]) => any) {
+  render(source: string, data: Data = {}, callback?: (...args: any[]) => any) {
     const ctx = this.context;
     const { config } = ctx;
     const { tag } = ctx.extend;
diff --git a/lib/hexo/router.ts b/lib/hexo/router.ts
index 9adfcece11..33edb61478 100644
--- a/lib/hexo/router.ts
+++ b/lib/hexo/router.ts
@@ -18,8 +18,6 @@ class RouteStream extends Readable {
   public _data: any;
   public _ended: boolean;
   public modified: any;
-  public push: any;
-  public emit: any;
 
   constructor(data: Data) {
     super({ objectMode: true });
diff --git a/lib/plugins/tag/code.ts b/lib/plugins/tag/code.ts
index 4d70b68ce9..e56e2122c4 100644
--- a/lib/plugins/tag/code.ts
+++ b/lib/plugins/tag/code.ts
@@ -30,8 +30,8 @@ const rCaption = /\S[\S\s]*/;
 function parseArgs(args: string[]): HighlightOptions {
   const _else = [];
   const len = args.length;
-  let lang, language_attr,
-    line_number, line_threshold, wrap;
+  let lang: string, language_attr: boolean,
+    line_number: boolean, line_threshold: number, wrap: boolean;
   let firstLine = 1;
   const mark = [];
   for (let i = 0; i < len; i++) {
@@ -123,7 +123,7 @@ export = (ctx: Hexo) => function codeTag(args: string[], content: string) {
     return `<pre><code>${escapeHTML(content)}</code></pre>`;
   }
 
-  let index;
+  let index: number;
   let enableHighlight = true;
 
   if ((index = args.findIndex(item => item.startsWith('highlight:'))) !== -1) {
diff --git a/lib/plugins/tag/post_path.ts b/lib/plugins/tag/post_path.ts
index 66c2b79704..fdc33eccab 100644
--- a/lib/plugins/tag/post_path.ts
+++ b/lib/plugins/tag/post_path.ts
@@ -9,7 +9,7 @@ import type Hexo from '../../hexo';
  *   {% post_path slug | title %}
  */
 export = (ctx: Hexo) => {
-  return function postPathTag(args) {
+  return function postPathTag(args: any[]) {
     const slug = args.shift();
     if (!slug) return;
 
diff --git a/lib/theme/index.ts b/lib/theme/index.ts
index 6553130a4e..aff5a74711 100644
--- a/lib/theme/index.ts
+++ b/lib/theme/index.ts
@@ -13,6 +13,7 @@ class Theme extends Box {
   public views: any;
   public i18n: I18n;
   public View: any;
+  public processors: any[];
 
   constructor(ctx: Hexo, options?) {
     super(ctx, ctx.theme_dir, options);
diff --git a/lib/theme/processors/config.ts b/lib/theme/processors/config.ts
index 64f65e2c28..c37f3ed13a 100644
--- a/lib/theme/processors/config.ts
+++ b/lib/theme/processors/config.ts
@@ -1,13 +1,15 @@
 import { Pattern } from 'hexo-util';
+import type { _File } from '../../box';
+import Theme from '..';
 
-function process(file) {
+function process(file: _File) {
   if (file.type === 'delete') {
-    file.box.config = {};
+    (file.box as Theme).config = {};
     return;
   }
 
   return file.render().then(result => {
-    file.box.config = result;
+    (file.box as Theme).config = result;
     this.log.debug('Theme config loaded.');
   }).catch(err => {
     this.log.error('Theme config load failed.');
diff --git a/lib/theme/processors/i18n.ts b/lib/theme/processors/i18n.ts
index ce955eb8a4..af2db9be95 100644
--- a/lib/theme/processors/i18n.ts
+++ b/lib/theme/processors/i18n.ts
@@ -1,11 +1,13 @@
 import { Pattern } from 'hexo-util';
 import { extname } from 'path';
+import type { _File } from '../../box';
+import type Theme from '..';
 
-function process(file) {
+function process(file: _File) {
   const { path } = file.params;
   const ext = extname(path);
   const name = path.substring(0, path.length - ext.length);
-  const { i18n } = file.box;
+  const { i18n } = (file.box as Theme);
 
   if (file.type === 'delete') {
     i18n.remove(name);
diff --git a/lib/theme/processors/source.ts b/lib/theme/processors/source.ts
index 40915fae47..ac8c21a1fe 100644
--- a/lib/theme/processors/source.ts
+++ b/lib/theme/processors/source.ts
@@ -1,7 +1,8 @@
 import { Pattern } from 'hexo-util';
 import * as common from '../../plugins/processor/common';
+import type { _File } from '../../box';
 
-function process(file) {
+function process(file: _File) {
   const Asset = this.model('Asset');
   const id = file.source.substring(this.base_dir.length).replace(/\\/g, '/');
   const { path } = file.params;
diff --git a/lib/theme/processors/view.ts b/lib/theme/processors/view.ts
index c4011564e2..c127d02e7c 100644
--- a/lib/theme/processors/view.ts
+++ b/lib/theme/processors/view.ts
@@ -1,15 +1,17 @@
 import { Pattern } from 'hexo-util';
+import type { _File } from '../../box';
+import type Theme from '..';
 
-function process(file) {
+function process(file: _File) {
   const { path } = file.params;
 
   if (file.type === 'delete') {
-    file.box.removeView(path);
+    (file.box as Theme).removeView(path);
     return;
   }
 
   return file.read().then(result => {
-    file.box.setView(path, result);
+    (file.box as Theme).setView(path, result);
   });
 }
 
diff --git a/lib/theme/view.ts b/lib/theme/view.ts
index 4b750a0960..af4c75be62 100644
--- a/lib/theme/view.ts
+++ b/lib/theme/view.ts
@@ -1,8 +1,10 @@
 import { dirname, extname, join } from 'path';
 import { parse as yfm } from 'hexo-front-matter';
 import Promise from 'bluebird';
+import type Theme from '.';
+import type Render from '../hexo/render';
 
-const assignIn = (target, ...sources) => {
+const assignIn = (target: any, ...sources: any[]) => {
   const length = sources.length;
 
   if (length < 1 || target == null) return target;
@@ -23,14 +25,12 @@ class Options {
 class View {
   public path: string;
   public source: any;
-  public _theme: any;
+  public _theme: Theme;
   public data: any;
   public _compiled: any;
   public _compiledSync: any;
   public _helper: any;
-  public _render: any;
-  public layout: any;
-  public _content: any;
+  public _render: Render;
 
   constructor(path: string, data) {
     this.path = path;
@@ -128,7 +128,7 @@ class View {
       text: this.data._content
     };
 
-    function buildFilterArguments(result) {
+    function buildFilterArguments(result: any): [string, any, any] {
       const output = render.getOutput(ext) || ext;
       return [
         `after_render:${output}`,