解决： 需要修改两个文件

// vue.config.js 注释掉 open: true
  publicPath: '/',
  outputDir: 'dist',
  assetsDir: 'static',
  lintOnSave: process.env.NODE_ENV === 'development',
  productionSourceMap: false,
  devServer: {
    port: port,
    // open: true,  注释掉本行
    overlay: {
      warnings: false,
      errors: true
    },
    before: require('./mock/mock-server.js')
  },

// package.json 在第二行代码中 加上  --open 否则一个窗口都不打开
  "scripts": {
    "dev": "vue-cli-service serve --open",
    "build:prod": "vue-cli-service build",
    "build:stage": "vue-cli-service build --mode staging",
    "preview": "node build/index.js --preview",
    "lint": "eslint --ext .js,.vue src",
    "test:unit": "jest --clearCache && vue-cli-service test:unit",
    "test:ci": "npm run lint && npm run test:unit",
    "svgo": "svgo -f src/icons/svg --config=src/icons/svgo.yml"
  },