In this paper, a composite anti-disturbance autopilot design for a missile system is proposed based on finite time integral sliding mode control scheme and nonlinear disturbance observer technique. First, a nonlinear disturbance observer is developed to estimate the external disturbances with partial known information. Second, in order to obtain good disturbance rejection performance and reject the other type of disturbances, a finite time integral sliding mode control strategy is employed to the design of a feedback controller. Third, an improved adaptive composite anti-disturbance autopilot is given to avoid the inaccuracy of the upper bound of external disturbances. Finally, simulation results are employed to demonstrate the effectiveness of the proposed method.