代码如下：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>获取鼠标在Canvas中的坐标位置</title>
<style>
#canvas{
border:1px solid #ccc;
width:300px;
height:300px;
overflow:hidden;
}
</style>
<script>
function get_canvas(ev,obj){
m_clientX = ev.clientX-obj.offsetLeft;
m_clientY = ev.clientY-obj.offsetTop;
document.getElementById("tips").innerHTML = "当前坐标：X："+ m_clientX + " ,Y：" +m_clientY;
}
</script>
</head>
<body>
<div id="tips"></div>
<div id="canvas" onmousemove="get_canvas(event,this)"></div>
</body>
</html>
兼容IE8+
原文：http://www.cnblogs.com/ifworld/p/7663574.html