Abstract: A mathematical model of single machine infinite bus system excitation control is established. An adaptive terminal sliding mode excitation controller is designed. By adding non linear function in the sliding surface, the convergence of error is sped up to achieve good control effect. Considering the uncertainties of disturbances, an adaptive identification of upper bound is designed, so that the controller has strong robustness. According to the Lyapunov theory, stability of this control system is proved. Simulation results show that the controller can improve the small signal and large disturbance stability of power system, and maintain the terminal voltage, which is better than the adaptive backstepping sliding mode excitation controller.