The invention relates to a trailing edge flap control method for relieving load fluctuation of a wind wheel of a floating type wind turbine. The method is used for relieving the power fluctuation caused by the floating type wind turbine platform movement; and according to six degrees of freedom (including longitudinal swinging, transverse swinging, vertical swinging, longitudinal shaking, transverse shaking and vertical shaking) of the platform movement, and measured data of other necessary parameters, the deflection angle of the wind turbine blade flap is determined, wherein the correspondingrelation between the six degrees of freedom and the relative speed (including the axial relative speed and the tangential relative speed) of a trailing edge flap, the corresponding relation between the axial relative speed and the deflection angle of the flap and the corresponding relation between the tangential relative speed and the deflection angle of the flap are involved. Through the adoption of the flap control method, the power fluctuation of the wind turbine caused by the platform movement can be effectively reduced, and the method has a good application prospect on the floating typeoffshore wind turbine.