Html:
<div id="MainContent"><img src="QQ截图20150515140512.png" width="" height=""></img></div>
</div>
CSS:
#MainContent {
display:table-cell;
width: 700px;
height: 800px; background: #0C78DD;
text-align:center;
vertical-align:middle; }
img 父元素有浮动属性的 话垂直对齐实现不了