<!DOCTYPE html>
<html>
<head>
<title></title>
<meta charset="utf-8">
<style type="text/css">
html{
height: 100%;
}
body{
height: 100%;
}
.i-body{
height: 100%;
}
/*需要从html开始一层层设置高度继承，否则无法获取高度*/
.i-body1{
height: 100%;
background: url('tiankong.jpg') no-repeat;
background-size: 100% 100%;
}
</style>
</head>
<body>
<div class="i-body">
<div class="i-body1"></div>
</div>
</html>