Intermediary physical isolation method and system applied to USB interface

The invention discloses an intermediary physical isolation method applied to a USB (Universal Serial Bus) interface. The intermediary physical isolation method comprises the following steps that: external USB equipment is connected into a security management and control module; a memory identification unit judges whether the external USB equipment is used authorization equipment or not, and sendsinformation to a management machine; the management machine receives the information and makes a verification judgment, and if the management machine is authorized equipment, the management machine passes the verification, and if the management machine is not authorized equipment, the management machine enters an intermediate detection module to detect permission; the intermediate detection moduletransmits authority detection information to the management machine; and the management machine receives the authority detection information, controls on-off of an internal switch of the security management and control module