The comprehensive evaluation method of thigh is proposed. The simulation model of the car frontal collision occupant restraint system is established by MADYMO simulation software. The reliability of the model is verified by experiments, and the thigh injury curve is benchmarked. In the above, the thigh injury was studied from the IP position, the angle of the occupant’s lower limb offset, and the angle between the lower leg and the floor. The results show that: ergonomics, while the IP position is located in the occupant’s knee, the team members have the least impact; the occupant’s lower limb bias angle is 12°. For the best position; reducing the angle between the calf and the floor can reduce the damage of the occupant’s thigh to varying degrees. Therefore, when the car collides, adjusting the relevant parameter parameters in advance can effectively reduce the risk of occupant injury, which is of great significance for the research and development of the car’s active safety.