Method for realizing circular file in media file

The invention belongs to the field of electric and digital data processing, in particular to a method for realizing a circular file in a media file system. The technical scheme adopted by the invention is that: three descriptions, such as LoopLength, Start Pointer and File Status are added into a new file description node i-node; the FileStatus comprises prewriting, loop writing and norm reading and writing; and prewriting, loop writing and norm reading and writing are sequentially carried out on the new file. The invention has the advantages that efficient reading and writing reduces repetitive deletion and copy; the hard disk is effectively protected to improve efficiency; and the method is suitable for reading and writing when a digital video recorder of security industry carries out 24 hours picture recording.