在网上找了很久，终于在一个百度问答里找到正确答案，记录下来，方便以后使用。在
<body>中设置：<body background="images\bg.jpg"
style=" background-repeat:no-repeat ;
background-size:100% 100%;
background-attachment: fixed;"
>
12345第一行是图片url第二行是背景图片不重复第三行是达到窗口的百分百比例第四行是图片固定，随着页面滚动而移动
<body background="https://api.qiuliqi.top/sp/"
style=" background-repeat:no-repeat ;
background-size:100% 100%;
background-attachment: fixed;"
>
<body background="https://qiuliqi.top/2233/dtbz.html"
style=" background-repeat:no-repeat ;
background-size:100% 100%;
background-attachment: fixed;"