For general software in the limitation of large and complex structures’ modeling, this article proposes a multi-software co-simulation technology. Hypermesh is a pre-processing software which can high-quality import and triangular CAD-models, taking advantage of this, the CAD-model of the car is meshed in Hypermesh. Using Matlab,the node coordinates data of each component’s elements are extracted from the grid data file outputted by Hypermesh, and are exported in the form of text file for Hfss to read.VBS program is used to build the finite element model, which is written in Matlab, then runs in Hfss to read the node coordinates data and form the initial triangular-mesh model of the Automobile. Considering only the interference of the ignition system power line’s common-mode current we simulated and analyzed the electric field distribution inside and outside of the automobile.This modeling method has a strong commonality ,and is a good reference for automobile EMC simulation modeling.