size();
window.onresize = function(){
size();
}
function size(){
var htnl_o=document.getElementsByTagName("html")[0];
htnl_o.style.fontSize = window.innerWidth/375*20 + "px";
console.log(htnl_o.style.fontSize);
}
原文：http://www.cnblogs.com/tongbiao/p/6623471.html