Electromagnetic compatibility of electric vehicles is withstanding great challenges because of multiple ECU and actuators distributed in vehicle. At present, researches on electromagnetic characteristics of vehicle mainly focus on rectification based on the EMC experiment, which take much time and energy. Thus, this paper adopts the way of computer simulation studying the electromagnetism model and electromagnetic characteristics of electric vehicle with following procedure. Firstly, the equivalent model of wiring harness was deduced and built. Harnesses were divided into different groups according to terminal reflection property. The equivalent unit parameter matrix was calculated to build the equivalent wiring harness. The crosstalk and radiation cases were set to check the equivalent harness method. In this way, the high voltage cables in motor drive system were simplified to be one to replace three phase cables and DC cables in electromagnetic model of vehicle, which decreases difficulty and workload in harness modeling. Next, the equivalent circuit model of motor drive system including models of IGBT, battery, high voltage harness and motor was built according to electromagnetic interference common code coupling path. The common mode current of DC bus end and three phase output terminal was simulated. The model was checked by conduction interference test of motor drive system. When it comes to vehicle body model, the groundbreaking method of reverse modeling is come up with. The body model was built according to four views drawing of vehicle, which is more simple and operational. This model simplified much unnecessary details to save simulating time and internal storage on the premise that the accuracy of simulation is guaranteed. At last, the electromagnetic radiation characteristics and distribution inside and outside vehicle were simulated by CST. The common mode choke coil is added and high voltage harness is shielded to optimize the electromagnetic compatibility.