According to Chinese economic development and human life improvement, the vehicle, as the most important transportation, goes into common people’s life gradually. The following problems of energy are highlighted day by day. In Chinese Manufacturing 2025, the idea of energy-saving and new energy vehicle was pointed out as an important development area, and energy-saving and emission reduction had already been the core work content for Original Equipment Manufacturers. Aerodynamic performance has great influence to vehicle handling performance, power performance, fuel and economy. The external flow filed character better or not will all impact vehicle comfort performance directly. Therefore, OEMs paid more and more attention to vehicle aerodynamic simulation analysis. Reasonable aerodynamic performance plays an important role in improving the performance of vehicle dynamics, economy and so on. Therefore, how to meet the requirements of modeling, engineering at the same time, but also to improve aerodynamic characteristics is particularly important for design a car. This paper discusses the factors that affect the air resistance of the car.