移动端rem，

rem布局 https://tgideas.qq.com/doc/frontend/spec/m/layout.html

<style>
    html {
     
     
      font-size: 100px;
    }
  </style>
  <script>
    //屏幕适应 
    (function (win, doc) {
     
     
      if (!win.addEventListener) return;
      var html = document.documentElement;
      function setFont() {
     
     
        var html = document.documentElement;
        var k = 750;
        var clientW = html.clientWidth > 750 ? 750 : html.clientWidth;
        html.style.fontSize = clientW / k * 100 + "px";
      }
      setFont();
      setTimeout(function () {
     
     
        setFont();
      }, 300);
      doc.addEventListener('DOMContentLoaded', setFont, false);
      win.addEventListener('resize', setFont, false);
      win.addEventListener('load', setFont, false);
    })(window, document);
  </script>