Abstract: Morphing wings can improve the aerodynamic performance of aircraft and expand the mission envelope. Elastic deformation based on the morphing structure can enable continuous and smooth shape change of the wings. It is an important approach for morphing wing structures. However, the morphing structure requires high energy consumption during structural deformation, leading to weight increase of the actuation system, causing the penalty to the performance benefits from morphing wings. To solve the problem, this study designs and validates an actuation system based on the energy balance principle to reduce the energy consumption, and decrease the size and weight of the actuation system. Initially, a negative stiffness mechanism based on the spiral pulley is designed, and its dynamic model is established and analyzed. Subsequently, an adjustment mechanism is introduced to enhance the adaptability of the negative stiffness mechanism, allowing it to satisfy the energy balance requirements under different structural stiffness better. Finally, the actuation system is integrated into a fishbone morphing wing and actuation experiments are performed. The experimental results demonstrate that the energy balance method can reduce the energy consumption of the drive system by 45%.