如果js设置移动端有两种方式 大家可以参考

//使用em单位
		var scaleObj = {
			documentEle :　document.documentElement,
			deviceWidth　: document.documentElement.clientWidth,
			scale : 0,
			resetPage :  function(){
				this.scale = this.deviceWidth/6.4;
				this.documentEle.style.fontSize = this.scale + 'px';
			},
			init :function(falseCode){
				this.ChangeDevW();
				this.deviceWidth < 640 ? this.resetPage() : falseCode;
			},
			ChangeDevW : function(){
				this.deviceWidth = this.documentEle.clientWidth;
			}
		};
		window.onload = function(){
			scaleObj.init(false);
		}
		window.onresize = function(){
			scaleObj.init(scaleObj.documentEle.style.fontSize = 625 + '%');
		};
		
		//使用px单位
		var vieWport = {
			phoneWidth : parseInt(window.screen.width),
			phoneScale : this.phoneWidth / 640,
			ua : navigator.userAgent,
			init : function(){
				 	if (/Android (\d+\.\d+)/.test(this.ua)) {
			        var version = parseFloat(RegExp.$1);
			        if (version > 2.3) {
			            document.write('<meta name="viewport" content="width=640, initial-scale= ' + this.phoneScale + ' ,minimum-scale = ' + this.phoneScale + ', maximum-scale = ' + this.phoneScale + ', target-densitydpi=device-dpi">')
			        } else {
			            document.write('<meta name="viewport" content="width=640, initial-scale= ' + this.phoneScale + ' , target-densitydpi=device-dpi">')
			        }
			    } else {
			        document.write('<meta name="viewport" content="width=640, user-scalable=no, target-densitydpi=device-dpi">')
			    }
			 }
		}

		vieWport.init();