Abstract: In vehicle EMC performance pre-evaluation and analysis, the size of the vehicle EM model defines the hardware requirement and time consumption, while the precision of the vehicle EM model defines the accuracy of the simulation result. However, model size and model precision are normally contradictory. In order to cut down the model size and keep the simulation result intact, a task oriented model simplification scheme is put forward. Roof-mounted FM antenna simulation is taken as an example task. Relationship between different metal parts on the vehicle body and the antenna pattern in XY plane is studied, and vehicle model simplification rules are proposed. An accordingly simplified hatchback model shows a reduction 34% in model size, 72% in analyzing time consumption, and 57% in memory requirement. The pattern distortion turns out to be as low as 0.2.