Abstract: This article conducts three-dimensional numerical simulation calculations on the effectiveness of using the method of local motion surface to improve the energy harvesting efficiency of wind turbines under small tip speed ratios. The results indicate that at low tip speed ratios, the use of local motion surface flow control on the surface of wind turbine blades can effectively suppress flow separation on the blade surface, significantly improving the energy efficiency of the wind turbine. By using the dynamic mode decomposition（DMD） method, the velocity fields around the original wind turbine and the wind turbine with local motion surface control applied to the blade surface were modal decomposed. By analyzing and comparing the flow field characteristics of each mode, it was found that the energy of the pulsating field in the wind turbine wake after active control was applied to the blades showed a significant change: the energy of the modes close to the main frequency of the wind turbine was significantly reduced, the modal energy of both single and double dominant frequencies has been reduced by up to 60%, effectively suppressing the high-energy structure of pulsating flow fields, thereby improving the aerodynamic performance of wind turbines and accelerating the recovery of wake behind them.