The invention discloses a USB interface hardware memory device with a loss log-off function and a realization method thereof, relating to the field of computer security and solving the existing problems such as unauthorized access and the potential security hazards after the loss of a USB Key. The USB interface hardware memory device comprises a USB interface circuit, a power supply circuit, a log-off circuit device, an encrypted CPU, a CPU peripheral circuit and a flash memory circuit. The log-off circuit is designed on hardware for being capable of realizing physical log-off; and as to software, memory area can be divided into a virtual drive, a hidden area and a memory area. Client software is stored in the virtual drive and prevented from being tampered. The log-off authority of a USB Key-B disk to a USB Key-A disk is written in the interior of a USB Key CPU through upper software so as to ensure the performability of the authority and simultaneously realize the pre-boot authentication of Windows.