<html>
<head>
<meta charset="utf-8" />
<title>Test</title>
<style>
#aa{ border:1px solid #ccc; height:400px; width:400px; text-align:center; margin:0 auto; }
#aa img{ vertical-align:middle; }
#aa span{ height:100%; width:0; overflow:hidden; display:inline-block; vertical-align:middle; }
</style>
</head>
<body>
<div id="aa" >
<img src="http://www.nbdy.cn/Public/default/images/logo.png"><span></span>
</div>
</body>
</html>
span不可少，是用来定位的