Abstract: In this paper,the rotor kinetic energy control is used and optimized to smooth the active power output of direct-drive permanent magnet synchronous generator（D-PMSG）. Firstly,the mechanism of power loss caused by rotor kinetic energy control is analyzed,based on which a power smoothing strategy is proposed to compensate the power loss. By analyzing the stability of wind turbine,the applicability of power smoothing strategy is obtained. Then,a fuzzy control algorithm（FLC）is used to optimize the control,which aims to improve the smoothness and the utilization of the output power,as well as to reduce the smoothness degradation caused by power command switching. At last,the effectiveness of the proposed control strategy and optimization algorithm is verified by Matlab/Simulink simulation.