Method for protecting cipher of USB interface

The invention discloses a method for protecting a cipher of a USB interface, which is to set a layer of USB filtration drive in an operation system, and set a protection cipher for the USB interface. The method comprises the following steps that: 1) the USB filter drive is used to determine that whether equipment accessing to the USB interface is storage equipment or not; 2) when the accessing equipment is the storage equipment, a user is required to input a cipher, if the cipher is matched with the set protection cipher, the operation system loads drive of the equipment for the user, if not,the drive of the equipment is not loaded; if the accessing equipment is non-storage equipment, the operation system directly loads the drive of the equipment for the user. Type of the USB equipment can be identified by the method, so that the storage type USB equipment can be used through the cipher, the user can conveniently use the storage type equipment without worrying about leakage of classified document in a compute