It was universally acknowledged that the engine is the core component for a racing car, and the exhaust part of the engine is one of the important factors affecting the engine power output. In previous races, teams used direct exhaust, but through simulation experiments, it can be found that this exhaust will cause torque loss at low speed. Therefore, some domestic schools have added the exhaust back pressure drum in the exhaust system, which solves the problem of torque loss at low speed. However, in the case of high engine speed and large exhaust volume, it will hinder the discharge of air flow and affect the engine power. For this reason, we plan to study the variable exhaust back pressure drum. Before that, this technology only appeared in F1 and some high-performance passenger cars, and has not been used in domestic FSC teams. This paper plans to design a variable back pressure device for the engine through CATIA, GT power and other modeling and simulation software. Through continuous optimization, the device can achieve the purpose of eliminating the above adverse effects and maximizing the engine power. At the same time, it pursues lower back pressure and quality of the exhaust pipe. Combined with the engine bench test, the reliability of the simulation results is analyzed assessment.