Abstract: Considering the strong aerodynamic damping characteristics of wind turbines,the tower fore-aft vibration and blade flapwise vibration are generally restrained. However,the tower lateral vibration is subjected to negligible aerodynamic damping,which may lead to large amplitudes disabling the wind turbine system. To solve this problem,a multiple tuned mass dampers（MTMD）system is designed in this paper to control the lateral structural vibration of spar-type offshore floating wind turbines. A simplified model of wind turbine coupled with MTMD system is constructed,and the parameters of dampers are optimized.Finally,simulations are performed for a combined wind-wave load case. Simulations shown the considerable mitigation effects of the proposed MTMD system on structural responses of the floating wind turbine in the edgewise direction.