<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>css实现背景图片自适应大小</title> </head> <body> <html> <style> body{ margin:0px; padding: 0px; width: 100%; height: 100%; } #bg_bg{ width: 100%; height: 100%; border : 0px red solid; background-image: url('https://ss0.baidu.com/-Po3dSag_xI4khGko9WTAnF6hhy/super/whfpf%3D68%2C40%2C50/sign=816023f01a178a82ce692ce0903e45b5/5bafa40f4bfbfbeda822ef437cf0f736afc31f96.jpg'); background-repeat: no-repeat; background-size: 100% 100%; } </style> <body> <div id="bg_bg"> </div> </body> </body> </html> <script> document.getElementById('bg_bg').style.height=document.body.scrollHeight+"px"; </script>