Abstract: Aiming at the operation complicated problem in the existing Nor Flash programming mode, this paper proposes a common method to online program Nor Flash directly through PC port which is based on DSU on-chip debug unit. In this method, Flash programming software reads the Nor Flash command sequences from a configuration file and data to be programmed of object files and through UART port sends to the DSU, then DSU programs Flash. And experimental results show that the method is easy to practice and has good universality.