Based on GB/T 18655—2018 standard， an experimental system was built for fuel cell vehicles’ DC/DC converter in an anechoic chamber. Conduction emission and radiation emission experiments were carried out. The interference current of each cable port and electric field intensity of the reference point was obtained during the normal operating state of fuel cell vehicles’ DC/DC converter. Then， an electromagnetic simulation model of fuel cell vehicles’ DC/DC converter was established based on the measured geometric parameters of each component in the experimental system. The obtained interference current from the conduction emission experiment was used as the excitation signal of the electromagnetic simulation model. The electric field intensity of the reference point position obtained by simulations was compared with the experimental results. The comparisons show that the overall change trend of simulation results is consistent with the overall change trend of the experimental results. The average error is about 5 dB in the high-frequency band， while the accuracy is relatively poor in the low-frequency band. Overall， the electromagnetic simulation model of the fuel cell vehicles’ DC/DC converter is reliable. Finally， the electromagnetic simulation model was used to analyze the radiation immunity characteristics of fuel cell vehicles’ DC/DC converters. The results show that the normal operating state of DC/DC converters will not be affected in the case of plane wave interference with the electric field strength of 30~100 V/m. Thus， the radiation immunity characteristics of fuel cell vehicles’ DC/DC converters meet the electromagnetic compatibility requirements.