BODY {
background-attachment: fixed;
background-image: url(您的图象地址) }

终于找到它了！好久了啊！
很 开始做了！
====================================================
最大化全屏

body{
background-color:#000;
background-image:url(b.jpg);
background-repeat: no-repeat;
background-position: 0% 26px;
background-attachment: fixed;
color:#FFFFFF;
overflow-x:hidden;
}