By coupling with cables, the high electromagnetic pulse poses a serious threat to the electronic control unit of vehicle platform, which affects the performance of the vehicle. Based on a typical vehicle platform, the effect mechanism of electronic control unit(ECU) in the environment of high electromagnetic pulses is analyzed. The relationship between the working state of the engine on the vehicle platform and the coupling voltage on the power supply line of the ECU is analyzed through the wide-band high electromagnetic pulse irradiation test of the vehicle platform. The test results show that the wide-band electromagnetic pulses cause electromagnetic interference to the vehicle ECU through the power cable, which leads to the engine flameout. According to the analysis results, a multi-level protection circuit is designed for the DC power supply of the ECU. The electromagnetic safety protection is realized by cutting off the transmission path of electromagnetic pulse energy, and the effectiveness of the protection circuit is verified.