<script type="text/javascript">

  var winWidth = document.documentElement.offsetWidth ||

  document.body.offsetWidth

  winWidth = winWidth < 1366 ? 1366 : winWidth

  var oHtml = document.getElementsByTagName('html')[0]

  oHtml.style.fontSize = 100 * winWidth / 1920 + 'px'

  window.addEventListener('resize', function () {

    var winWidth = document.documentElement.offsetWidth || document.body.offsetWidth

    winWidth = winWidth < 1400 ? 1400 : winWidth

    var oHtml = document.getElementsByTagName('html')[0]

    oHtml.style.fontSize = 100 * winWidth / 1920 + 'px'

  })

</script>

所测的尺寸去除以100就可以转化位rem