1.找到build/utils.js
2.在exports.cssLoaders内添加如下代码

const postcssLoader = {
    loader: 'postcss-loader',
    options: {
      sourceMap: options.sourceMap
    }
}

function generateLoaders (loader, loaderOptions) {
    const loaders = [cssLoader]
    if (loader) {
      loaders.push({
        loader: loader + '-loader',
        options: Object.assign({}, loaderOptions, {
          sourceMap: options.sourceMap
        })
      })
    }
    loaders.push(postcssLoader)
    ......
}

3.在项目目录下也就是与node_modules同级目录下新建 .postcssrc.js (注意前面有个点) 添加如下代码

// https://github.com/michael-ciniawsky/postcss-load-config

module.exports = {
  "plugins": {
    "postcss-import": {},
    "postcss-url": {},
    // to edit target browsers: use "browserslist" field in package.json
    "autoprefixer": {}
  }
}

4.找到package.json文件添加如下代码 （注意：与devDependencies字段同级）

"browserslist": [
    "last 10 Chrome versions",
    "last 5 Firefox versions",
    "Safari >= 6",
    "ie > 8"
  ]

5.安装如下依赖

npm install postcss-import --save-dev
npm install postcss-loader --save-dev
npm install postcss-url --save-dev
npm install autoprefixer --save-dev

6.这时可以启动你的工程了 试试吧