Deu to the distinctive flight characteristics of high-performance aircrafts, the models have strong non-linearity and the parameters have strong coupling, which brings a challenge to the design of flight controllers.When designing the controller of the nonlinear system, the traditional method of sliding mode control has the advantages of easy implementation and strong robustness, but the chattering of system states is likely to appear, which may weaken the efficiency of the controller.To solve the above problems, a sliding mode controller with unidirectional auxiliary surface based on the fast double-power reaching law is proposed, and the conditions of convergence are proved.The longitudinal model of the aircraft is divided into four control loops, which are the loops of altitude, velocity, attitude angle and angular speed of attitude, and the controller for each loop is designed respectively.Simulation results show that the proposed design method of flight controllers can effectively control the longitudinal state of the aircraft, and can effectively suppress the chattering.