npm install --save-dev postcss-loader

{
 test:/\.css$/,
 use:[
  'style-loader','css-loader?importLoaders=1','postcss-loader' 
 ] 
}

module.exports = {
  plugins: [
    require('autoprefixer')({ /* ...options */ })
  ]
}

module.exports = {
  plugins: [
    new webpack.LoaderOptionsPlugin({
      options: {
        postcss: function(){
          return [
            require("autoprefixer")({
              browsers: ['ie>=8','>1% in CN']
            })
          ]
        }
      }
    })
  ]
}