CSS

div{
    width:200px;
    height:200px;
    border:1px solid red;
    text-align:center;
    line-height:200px;
}

img{
    vertical-align:middle;
}

HTML

<div>
    <img src="http://dummyimage.com/150x150/000/fff&text=dummy" >
</div>

检查此 http://jsfiddle.net/dP89y/