In the practical application of wireless power transmission technology for unmanned aerial vehicles(UAVs), inaccuracies in positioning and docking control during UAV landing can lead to errors in docking position and displacement. Due to the small size of the UAV, the coupling mechanism’s size is also limited, and any offset at this time can reduce the coupling efficiency of coupling mechanism, which in turn leads to the reduction of the efficiency of the wireless power transmission system, affecting its normal operation. Therefore, to improve the system’s anti-offset characteristics, it is necessary to design and optimize the coupling mechanism of the UAV wireless charging system. This study analyzes and compares the coupling characteristics of different coupling mechanisms with considering consistent line usage and the structural characteristics of UAVs. A suitable coupling mechanism for UAVs is then designed and the parameters of the coupling mechanism are optimized for lightweight, using M/l as the optimization goal. Finally, the feasibility of optimization method for the coupling mechanism is verified by simulation and experiment.