Aiming at the problem that it is difficult to evaluate the error between the simulation and the actual measurement of the radiated emission of the DCDC converter for fuel cells, an analysis method for quantitatively evaluating the simulation accuracy of radiated emission is proposed. According to the test setup for the radiation emission of the fuel cell DCDC converter, the cable current was collected as the disturbance source current. A simulation platform for the radiation emission of the DCDC converter was built in the FEKO software. The simulation method was verified by comparing the simulation results with the measured ones. Then, an analysis method was proposed to quantitatively analyze the simulation and measurement errors from two aspects: the sawtooth peak frequency doubling error and the trend error. Evaluation indicators for the simulation accuracy were formulated. The error parameters were statistically analyzed to evaluate the simulation accuracy quantitatively. The research shows that the simulation and the measured results have a good consistency in the frequency doubling error of the sawtooth peak, and there are some deviations in the trend error. The actual error can be corrected by the research method in the future, indicating that the proposed method can accurately analyze the error and evaluate the simulation accuracy more accurately. Therefore, the electromagnetic compatibility performance of DCDC converter can be predicted by using the method of harassing source current loading, which can quickly predict the radiation emission level of components, thus reducing the test cost.