To obtain higher accelerator beam quality and operating efficiency, the performance of the power supply system often plays an important role. In view of the continuous updating of power electronic devices and the requirements of system integration miniaturization, the electromagnetic interference of power system is becoming more and more serious. Strong electromagnetic interference will affect the stable operation of other sensitive systems of the accelerator system, and even reduce the beam quality. In this paper, the transient response of accelerator power switching points is studied, including surge and ringing. Through the calculation and experimental verification of the potential mode of the circuit, the main interference sources were analyzed. Design of power switch interference filter effectively restrains electromagnetic interference of power supply.