Aiming at the problem that the aircraft is subject to complex disturbances during flight, this paper proposes an improved adaptive control method and applies it to the airflow angle control of the F-16 aircraft. Based on the adaptive backstepping method, the method uses Fourier Series to decompose the nonlinear modeling errors and complex disturbances of the flight control system. Then the coefficients of each Fourier Series component are estimated. Finally, the estimated coefficients of each component are synthesized to obtain an estimated value of the complex perturbation. Therefore, an improved adaptive method based on the Fourier Series is proposed. This method addresses fast time-varying disturbance that cannot be dealt with by traditional methods. Finally, the simulation experiment demonstrates that the improved control approach has a better effect on complex disturbances than the traditional adaptive backstepping method.