diff --git a/README.md b/README.md
index 21a16c5..d34825f 100644
--- a/README.md
+++ b/README.md
@@ -95,7 +95,8 @@ Default:
   fontViewportUnit: 'vw',  // vmin is more suitable.
   selectorBlackList: [],
   minPixelValue: 1,
-  mediaQuery: false
+  mediaQuery: false,
+  exclude: [] // ignore some files
 }
 ```
 - `unitToConvert` (String) unit to convert, by default, it is px.
@@ -111,6 +112,9 @@ Default:
         - `[/^body$/]` will match `body` but not `.body`
 - `minPixelValue` (Number) Set the minimum pixel value to replace.
 - `mediaQuery` (Boolean) Allow px to be converted in media queries.
+- `exclude` (Array or Regexp) Ignore some files like 'node_modules'
+    - If value is regexp, will ignore the matches files.
+    - If value is array, the elements of the array are regexp.
 
 ### Use with gulp-postcss
 
diff --git a/index.js b/index.js
index 7bcc46a..27c4442 100755
--- a/index.js
+++ b/index.js
@@ -29,8 +29,22 @@ module.exports = postcss.plugin('postcss-px-to-viewport', function (options) {
   var pxRegex = new RegExp('"[^"]+"|\'[^\']+\'|url\\([^\\)]+\\)|(\\d*\\.?\\d+)' + opts.unitToConvert, 'ig')
 
   return function (css) {
-
+    
     css.walkDecls(function (decl, i) {
+      
+      // Add exlclude option to ignore some files like 'node_modules' 
+      if (opts.exclude && decl.source.input.file) {
+        if (Object.prototype.toString.call(opts.exclude) === '[object RegExp]') {
+          if (!handleExclude(opts.exclude, decl.source.input.file)) return;
+        } else if (Object.prototype.toString.call(opts.exclude) === '[object Array]') {
+          for (let i = 0; i < opts.exclude.length; ++i) {
+            if (!handleExclude(opts.exclude[i], decl.source.input.file)) return;
+          }
+        } else {
+          throw new Error('options.exclude should be RegExp or Array!');
+        }
+      }
+      
       // This should be the fastest test and will remove most declarations
       if (decl.value.indexOf(opts.unitToConvert) === -1) return;
 
@@ -51,6 +65,14 @@ module.exports = postcss.plugin('postcss-px-to-viewport', function (options) {
   };
 });
 
+function handleExclude (reg, file) {
+  if (Object.prototype.toString.call(reg) !== '[object RegExp]') {
+    throw new Error('options.exclude should be RegExp!');
+  }
+  if (file.match(reg) !== null) return false;
+  return true;
+} 
+
 function getUnit(prop, opts) {
   return prop.indexOf('font') === -1 ? opts.viewportUnit : opts.fontViewportUnit;
 }
diff --git a/spec/px-to-viewport.spec.js b/spec/px-to-viewport.spec.js
index 23632e2..aad1213 100644
--- a/spec/px-to-viewport.spec.js
+++ b/spec/px-to-viewport.spec.js
@@ -196,3 +196,51 @@ describe('minPixelValue', function () {
       expect(processed).toBe(expected);
   });
 });
+
+describe('exclude', function () {
+  var rules = '.rule { border: 1px solid #000; font-size: 16px; margin: 1px 10px; }';
+  var covered = '.rule { border: 1px solid #000; font-size: 5vw; margin: 1px 3.125vw; }'
+  it('when using regex at the time, the style should not be overwritten.', function () {
+    var options = {
+      exclude: /node_modules/
+    }
+    var processed = postcss(pxToViewport(options)).process(rules, {
+      from: '/node_modules/main.css'
+    }).css;
+
+    expect(processed).toBe(rules);
+  });
+
+  it('when using regex at the time, the style should be overwritten.', function () {
+    var options = {
+      exclude: /node_modules/
+    }
+    var processed = postcss(pxToViewport(options)).process(rules, {
+      from: '/example/main.css'
+    }).css;
+
+    expect(processed).toBe(covered);
+  });
+
+  it('when using array at the time, the style should not be overwritten.', function () {
+    var options = {
+      exclude: [/node_modules/, /exclude/]
+    }
+    var processed = postcss(pxToViewport(options)).process(rules, {
+      from: '/exclude/main.css'
+    }).css;
+
+    expect(processed).toBe(rules);
+  });
+
+  it('when using array at the time, the style should be overwritten.', function () {
+    var options = {
+      exclude: [/node_modules/, /exclude/]
+    }
+    var processed = postcss(pxToViewport(options)).process(rules, {
+      from: '/example/main.css'
+    }).css;
+
+    expect(processed).toBe(covered);
+  });
+});