diff --git a/bower.json b/bower.json
index 602446e0..4d496482 100644
--- a/bower.json
+++ b/bower.json
@@ -1,6 +1,6 @@
 {
   "name": "simditor",
-  "version": "2.3.16",
+  "version": "2.3.17",
   "homepage": "http://simditor.tower.im/",
   "authors": [
     "farthinker <farthinker@gmail.com>"
diff --git a/lib/simditor.js b/lib/simditor.js
index 6a5a931d..cb00cdac 100644
--- a/lib/simditor.js
+++ b/lib/simditor.js
@@ -1,8 +1,3 @@
-/*!
-* Simditor v2.3.16
-* http://simditor.tower.im/
-* 2018-06-14
-*/
 (function (root, factory) {
   if (typeof define === 'function' && define.amd) {
     // AMD. Register as an anonymous module unless amdModuleId is set
@@ -2354,6 +2349,7 @@ Clipboard = (function(superClass) {
           pasteContent = $('<div/>').append(_this._pasteBin.contents());
           pasteContent.find('style').remove();
           pasteContent.find('table colgroup').remove();
+          _this._cleanPasteFontSize(pasteContent);
           _this.editor.formatter.format(pasteContent);
           _this.editor.formatter.decorate(pasteContent);
           _this.editor.formatter.beautify(pasteContent.children());
@@ -2493,6 +2489,22 @@ Clipboard = (function(superClass) {
     return this.editor.inputManager.throttledValueChanged();
   };
 
+  Clipboard.prototype._cleanPasteFontSize = function(node) {
+    var $node, sizeMap;
+    $node = $(node);
+    if (!($node.length > 0)) {
+      return;
+    }
+    sizeMap = ['1.5em', '1.25em', '0.75em', '0.5em'];
+    return $node.find('[style*="font-size"]').map(function(i, el) {
+      var $el;
+      $el = $(el);
+      if ($.inArray($el.css('font-size'), sizeMap) < 0) {
+        return $el.css('font-size', '');
+      }
+    });
+  };
+
   return Clipboard;
 
 })(SimpleModule);
diff --git a/package.json b/package.json
index e3383583..56b6f93a 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "simditor",
-  "version": "2.3.16",
+  "version": "2.3.17",
   "description": "A simple online editor",
   "keywords": "editor simditor",
   "repository": {
diff --git a/site/assets/scripts/simditor.js b/site/assets/scripts/simditor.js
index 2497c379..cb00cdac 100644
--- a/site/assets/scripts/simditor.js
+++ b/site/assets/scripts/simditor.js
@@ -2349,6 +2349,7 @@ Clipboard = (function(superClass) {
           pasteContent = $('<div/>').append(_this._pasteBin.contents());
           pasteContent.find('style').remove();
           pasteContent.find('table colgroup').remove();
+          _this._cleanPasteFontSize(pasteContent);
           _this.editor.formatter.format(pasteContent);
           _this.editor.formatter.decorate(pasteContent);
           _this.editor.formatter.beautify(pasteContent.children());
@@ -2488,6 +2489,22 @@ Clipboard = (function(superClass) {
     return this.editor.inputManager.throttledValueChanged();
   };
 
+  Clipboard.prototype._cleanPasteFontSize = function(node) {
+    var $node, sizeMap;
+    $node = $(node);
+    if (!($node.length > 0)) {
+      return;
+    }
+    sizeMap = ['1.5em', '1.25em', '0.75em', '0.5em'];
+    return $node.find('[style*="font-size"]').map(function(i, el) {
+      var $el;
+      $el = $(el);
+      if ($.inArray($el.css('font-size'), sizeMap) < 0) {
+        return $el.css('font-size', '');
+      }
+    });
+  };
+
   return Clipboard;
 
 })(SimpleModule);
diff --git a/src/clipboard.coffee b/src/clipboard.coffee
index 2a4d7865..0444ce24 100644
--- a/src/clipboard.coffee
+++ b/src/clipboard.coffee
@@ -94,9 +94,11 @@ class Clipboard extends SimpleModule
         pasteContent = $('<div/>').append(@_pasteBin.contents())
         pasteContent.find('style').remove() # clear style tag
         pasteContent.find('table colgroup').remove() # clear table cols width
+        @_cleanPasteFontSize pasteContent
         @editor.formatter.format pasteContent
         @editor.formatter.decorate pasteContent
         @editor.formatter.beautify pasteContent.children()
+
         pasteContent = pasteContent.contents()
 
       @_pasteBin.remove()
@@ -209,3 +211,20 @@ class Clipboard extends SimpleModule
       @editor.selection.setRangeAtEndOf(pasteContent.last())
 
     @editor.inputManager.throttledValueChanged()
+
+  _cleanPasteFontSize: (node) ->
+    $node = $(node)
+    return unless $node.length > 0
+
+    sizeMap = [ 
+      '1.5em'
+      '1.25em'
+      '0.75em'
+      '0.5em'
+    ]
+
+    $node.find('[style*="font-size"]')
+      .map (i, el) ->
+        $el = $(el)
+        if $.inArray($el.css('font-size'), sizeMap) < 0
+          $el.css('font-size', '')
diff --git a/styles/simditor.css b/styles/simditor.css
index 218df4af..08f3048d 100644
--- a/styles/simditor.css
+++ b/styles/simditor.css
@@ -1,7 +1,7 @@
 /*!
-* Simditor v2.3.16
+* Simditor v2.3.17
 * http://simditor.tower.im/
-* 2018-06-14
+* 2018-07-23
 */
 @font-face {
   font-family: 'Simditor';