In order to ensure the flight stability of aircraft during changing the sweep angle， a retrofit control method based on the receding horizon optimal (RHO) algorithm is proposed. Firstly， the nominal control law is designed by the backstepping technique， which is used to provide the basic flight stability as well as the tracking performance. Secondly， the transfer functions of the command filters are transformed into the state space form， and an augmented state equation is obtained based on the state equations of the aircraft， command filters and integral tracking error. Then， the retrofit control law is designed by RHO algorithm. In order to ensure the flight stability in the process of changing the sweep angle rapidly， the retrofit value is calculated within a finite horizon to compensate for the nominal controller in real-time. Finally， the effectiveness of the designed control method is tested through the simulations of the flight path angle control system.