Abstract: Utilizing a hybrid algorithm of "multilevel fast multipole algorithm(MLFMA) plus multi-conductor transmission line theory(MTL)" and its measurement method respectively, we study the suppression of the electromagnetic radiations of the cables in the payload module by using the multi-point grounding. MTL is employed to quickly calculate the leakage currents in the region of the cable, which could be used as the excited currents, and then MLFMA is used to accurately and efficiently simulate the radiations of the cables in the payload module corresponding to different grounding points in resonant and non-resonant respectively. The measured results and the simulated results verify the accuracy and the high efficiency of the hybrid algorithm. In conclusion, the radiations of the cables in non-resonant in the payload module can be reduced distinctively by using the multi-point grounding, in order to optimize the complex electromagnetic environment in the payload module. The research can provide theoretical guidance for the engineering design on the aerospace electromagnetic compatibility.