Through the profoundly and broadly studies of birds, changes in avian wings during flight tend to be combinations of multiple morphing modes. Such kind of multi-joint wing offers morphing aircraft an effective approach for solving the problem of mass center shift in longitudinal trim and control system design during the morphing process. However, the influence of morphing on control surface efficiency of biomimetic wing aircraft is not well understood. Therefore, a two-joint wing morphing UAV with asymmetric sweep angle change and flexible trailing edge deflection as redundant lateral control surface is designed in this study. Dynamic responses of targeted UAV under different mass ratio of inner and outer wing are analyzed in two typical missions based on Kane dynamic model. A numerical method based on unsteady vortex-lattice methods is established for analyzing the efficiency of redundant control surfaces from both the perspective of aerodynamic change and aerodynamic energy consumption. Analysis results show that this biomimetic morphing mode can significantly improve the mission execution efficiency and reduce the difficulty of control system design of targeted UAV. Generalized control surface of sweep angle has higher control efficiency in large angular velocity and lift situation. With asymmetric sweep angle change as a new lateral control surface, the convergence time for roll maneuver is greatly reduced and the stability of system is enhanced, but the cumulative aerodynamic energy consumption and requirement for actuators output power also increase. Distribution of aerodynamic energy consumption in wing spanwise direction can provide theoretical support for actuator selection and reasonable distribution.