Using the parallel computing characteristics of FPGA, the FPGA can realize the nanosecond simulation step size in the real time simulation of power electronic devices and models, which can show the characteristic of power electronic switching devices more reality. Through the analysis of the buck converter in inductor current continuous mode of mathematical model, with the Xilinx system generator tools we built the mathematical model of the buck converter, and carries on the realtime simulation, and compared with device simulation results, from the simulation results, it can be seen the effectiveness of the mathematical and can replace the device model of Buck converter in a certain error range, and also for the actual circuit design and debugging provides a way.