To assess the susceptibility of road vehicles in complex electromagnetic environments, this paper proposes a radiation immunity testing method of vehicles based on actual electromagnetic environments in reverberation chambers (RCs), which records the actual electromagnetic signals, constructs a complex signal playback system in an RC, and gives the cumulative distribution function (CDF) of the received power. Moreover, this paper provides a field strength calibration method and the radiation immunity testing in an RC. The radiation immunity testing of vehicle was conducted, and the results show that in the complex RC electromagnetic environment, some vehicles have electromagnetic safety risks. The study method provides important support for enterprises to evaluate the electromagnetic compatibility quality of vehicles.