Aiming at UAV trajectory tracking control under conditions of external disturbance, output constraints and partial model unknown, the backstepping ADRC strategy based on output constraints is proposed. Firstly, the UAV dynamics model is transformed into a form with external disturbances and meets the design requirements of backstepping. The unknown part of the model is approximated by neural network. Then, the controller is designed using the backstepping method, and ADRC algorithm is introduced to combine with the controller designed by the backstepping method to form the backstepping ADRC controller, and the value of the output is guaranteed to be in the upper and lower limits of the constraints by introducing obstacle Lyapunov function, and the stability analysis can prove the boundedness of the tracking error of the designed controller. Finally, the convincingness of the designed strategy was effective over Simulation.