这个效果还不错
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
*{margin: 0;padding: 0}
.box1{ 400px;height: 255px;border: 1px solid #ccc;margin:60px;position: relative;}
.box2{ 400px;height: 300px;border: 1px solid #ccc;position: absolute;overflow: hidden;top:0;left: 500px;margin: 50px}
.box2>img{position:absolute;}
.fu{ 160px;height: 120px;background:#ffffcc;border: 1px solid #ccc;position: absolute;opacity: 0.5;}
</style>
</head>
<body>
<div class="magnifier">
<div class="box1">
<div class="fu"></div>
<img src="http://cdn.attach.qdfuns.com/notes/pics/201708/07/144141buvdo9pxfhfxfxuo.jpg" alt="">
</div>
<div class="box2">
<img src="http://cdn.attach.qdfuns.com/notes/pics/201708/07/144134kfyiyiy14chyyydi.jpg" alt="">
</div>
</div>
<script src="http://code.jquery.com/jquery-1.8.0.min.js"></script>
<script>
$(function(){
//初始化
$(".fu,.box2").hide();
$(".box1").hover(function(){
$(".fu,.box2").show();
},function(){
$(".fu,.box2").hide();
});
$(".box1").mousemove(function (e) {
//元素距离浏览器的位置
var ex=e.pageX;
var ey= e.pageY;
//获得到box1的偏移量
var boxx=$(this).offset().left;
var boxy=$(this).offset().top;
////获得到浮窗的宽高
var fuw=$(".fu").width();
var fuh=$(".fu").height();
//获得box的宽高
var boxw=$(this).width();
var boxh=$(this).height();
//获得box2的宽高
var box2w=$(".box2").width();
var box2h=$(".box2").height();
//获得放大的img的宽高
var imgw=$(".box2>img").width();
var imgh=$(".box2>img").height();
//求得偏移量
var left=ex-boxx-fuw/2;
var top=ey-boxy-fuh/2;
//判断边界区域
if(left<0){
left=0;
}else if(left>(boxw-fuw)){
left=boxw-fuw;
}
if(top<0){
top=0;
}else if(top>boxh-fuh){
top=boxh-fuh;
}
//求得比率
var psx=left/(boxw-fuw);
var psy=top/(boxh-fuh);
; $(".fu").css({"left":left,"top":top});
$(".box2>img").css({"left":-psx*(imgw-box2w),"top":-psy*(imgh-box2h)});
});
});
</script>
</body>
</html>