Abstract: Aiming at the problems of low control accuracy, poor robustness, and slow response of the ball and plate system, an optimal backstepping sliding mode control scheme is proposed based on the new reaching law. Firstly, the sliding mode surface is designed by tracking error and virtual control quantity. Secondly, backstepping and sliding mode control are combined, and a new reaching law is designed, which creates the controller. Then, the stability of the whole system is proved by the Lyapunov theory. Finally, this paper finds a set of optimal parameters of the new reaching law by improving the Particle Swarm Optimization (PSO) algorithm to achieve optimal control. The simulation results show that the proposed control strategy can eliminate errors and improve control accuracy. The system adjustment time is 0.2 s, which can speed up the system's response speed. It enhances its robustness and restricts the chattering engendered by the system. These results verify the feasibility of the proposed control scheme.