Abstract: The generation process, propagation mechanism and the impact on the switching power supply of the single event transient effect in the PWM (pulse width modulator) are analyzed in this paper. Combined with the technical characteristics of the satellite payload’s dedicated power supply, an effective protection strategy is proposed. The correctness of the mechanism analysis and the effectiveness of the improvement measures is verified by the pulsed laser and heavy ion test methods. It provides new ideas for eliminating the major hidden dangers of such devices in space applications.