The existing web prevent tampering and automatic recovery technology mainly have three at present: time polling technology, event trigger technology + core embedded technology, file filtering technology + event trigger technology. All the three ways monitor the target file when the target file is tampered, it will return to the original condition from backup files in the file, but the backup files weren't protected, if the backup files were destroyed, the web pages won't be returned to its original condition. So in file filtering + event trigger technology foundation, this paper studies how to use MD5 calibration, DES encryption, file renaming, three ways to protect the safety of backup files.