Getting the fastest speed is a main goal of the racing car, therefore the working condition is fierce in the auto racing. In this process, tires have large degree of deformation because of the low rigidity of tire and high lateral acceleration of vehicle for racing car in steering. Thus, traditional Ackerman geometry cannot meet the requirement of smooth steering and small eccentric wear of tire in the design of racing steering system. For solving these above problems, a design method of racing car steering system based on the compensation of four tires’ deformation is put forward. First, the mathematical model of the steering trapezoid is established based on the Plane Geometry to obtain the influence of the racing car steering system structural parameters on the angle relation of the inner wheel and outer wheel. Then, on the basis of the simulation data of vehicle performance parameters in the specific circuit by racing car driving simulator, the target rotation angle relation of the inner wheel and outer wheel is obtained by the processing. Last, the steering system structural parameters are optimized based on the Least Squares Algorithm. In the process of the racing car steering, the instantaneous shafts of each wheel are not coincident because of the independence of the suspension system and the relative independence of the motion of each wheel. This feature is particularly evident in the working condition of variable and fierce race. This paper also defines the concept of instantaneous corner radius, and put forward an analysis method of transient -state response to evaluate the design method of racing car steering system. The simulation results show that the design method of steering system can effectively improve the transient response characteristic of the racing car, and reduce the tire eccentric wear.