Continuous Data Protection is a data recovery method which can protect file systems against malicious attacks or users’ mistakes. This paper proposes BCFBS (BUPT Continuous File Backup System): a continuous data protection architecture at file level. Compared with other approaches, it uses caching technique to protect the consistence between file versions, thereby speeding up both the backup of file version and space recycling. Furthermore, BCFBS combines techniques of filter the type of file, adjusting the frequency of the backup of file with incremental backup to make up the storage waste default of traditional CDP. Experimental results demonstrate that BCFBS can save storage space by 50%.