Abstract: In order to solve the problem of software upgrading of on-board equipment of train, this paper studied the technology of software upgrading of on-board equipment of train based on USB, and put forward a method of offline software upgrading of on-board equipment with faster transmission speed, higher stability and more convenient operation.This method was based on IAP (In Application Programming) technology, with flash inside the processor as the storage carrier, and the bottom package program based on USB communication protocol was used to upgrade the software of the equipment.This technology has been applied to the software upgrade of on-board equipment such as fault diagnosis, which effectively improves the efficiency of software upgrade.