Abstract: This invention discloses a method for backup and recovery of the long filename in the computer system (e.g., DOS) that not support the long filename. The technique of the backup operation of this invention is to read the file directory table (FDT) from the logic partition of the hard disk by calling the basic input output system (BIOS) function; then transfer the long filename and short filename items into long filename format and saving to a backup file. Alternatively, recovering the backup is to search the short filename of each directory and sub directory and obtaining the data in the back up file; then write the matched long filename back to the original FDT.