The time-domain near-field simulation of electromagnetic compatibility has attracted more and more attention in industrial application. The physical characteristics of the automotive electronic fan drive circuit are complex, and the time-domain simulation has the problem of excessively long calculation time under the condition of steep pulse signal excitation. First, the waveform oscillation problem of time-domain finite element calculation is analysed and verified. The limitations of the classical time-frequency domain calculation method of radiated electric field in practical application are also considered. Secondly, the suppression effect of different window functions on the spectrum leakage of steep pulse signals under incoherent sampling conditions are compared and studied. The cubic spline interpolation is used to weaken the fence effect. Based on the Rife-Vincent ( Ⅲ) window Fourier transform and cubic spline, the time-frequency domain calculation method of radiated electric field is established. Finally, the rapid calculation of the timedomain radiated electric field of the car fan drive circuit is realized, which avoids the numerical oscillation problem in the initial stage of the time-domain calculation. Compared with the traditional time-domain calculation method, the calculation time is reduced by about 62% under the condition of non-parallel calculation. The method in this article provides conditions for parallel computing and has the potential to reduce computing time consumption by several to tens of times.