The variable structure roll autopilot is designed with reaching law approach. Aiming at solving the chattering problem caused by sign function, the saturation function is introduced. In order to improve the system, a new reaching law is proposed on the basis of the conventional exponential reaching law. Furthermore, to prove the efficiency of the variable structure control autopilot, a classical autopilot is also designed. Simulation results indicate the efficiency of variable structure control autopilot, and the new reaching law improves the system more