Abstract: A robust adaptive backstepping sliding mode control (SMC) method is proposed for a class of unmatched uncertain nonlinear systems. In the procedure of controller design, model uncertainty and unknown external disturbances are considered. In order to simplify the controller, dynamic surface strategy is adopted during the backstepping. The chattering of control signals is effectively suppressed by the employment of the hyperbolic tangent function and attenuation factor. An adaptive law is designed to strengthen the system robustness for modelling error. The stability of the system is ascribed to the design of an n-order positive symmetrical matrix. The proposed control method is applied to the F-8 aircraft longitudinal dynamical model. The simulation results demonstrate that the proposed method can be effectively applied to the control of aircraft trajectory tracking.