<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <style> body{ background-image: url(123.jpg); background-repeat: no-repeat; } </style> </head> <body> <script> function init(){ document.body.style.backgroundSize="100% "+document.documentElement.clientHeight+"px"; } init(); window.onresize = function(){ init() } </script> </body> </html>
document.documentElement.clientHeight指的是浏览器的可见高度
onresize是浏览器高度和宽度发生改变
原文：http://www.cnblogs.com/shuaihan/p/7267591.html