Abstract: A method of encrypting/decrypting the document and a safety management storage device and system method of its safety management, using for the safety management of electronic documents, the said system comprising a PC or mainframe installed with common reading software and a storage device of safety management connected to the said PC/mainframe through hot-plug; when connected to the mainframe, the said storage device is enumerated as a USB CDROM device at least. The user owns the said storage device can encrypt the electronic documents by using the encryption keys to generate an encrypted document with the same file type, also can open the encrypted document by using common reading software, and then use the document according to the predetermined operation authority.