When typical pitch control widely applied to onshore wind turbinesis applied to a floating wind turbine,the tower oscillation of the floating wind turbine is increased by the rotor thrust change.This phenomenon is called negative damping,and it causes instability in the power produced and decreases the fatigue life of the wind turbine.Therefore,the establishment of a control method which can suppress tower motion and power variation is an important issue.The NMRI (National Maritime Research Institute) in Japan proposed a new control method restraining negative damping,which is called as RTS control in this study.The concept of RTS control is to control the blade pitch by the rotor speed and the tower pitch anglular velocity.The purpose of this study is to apply RTS controlto a floating wind turbine and verify the effect on tower oscillation,power,and fatigue load.To evaluate the control system,the numerical simulation software FAST developed by NREL (National Renewable Energy Laboratory) was used for the aeroelastic analysis,and WAMIT developed by MIT was used to analyze the interactions of the waves and wind turbines.As a simulation model,the 5 MW wind turbine with the spar-type floating platform model developed by Jonkman was used.Our study showed that RTS control can restrain negative damping and decrease fatigue load in the blade root and the tower base.