A wind-hydro power generation system and its power generation method which use both wind power and hydraulic power. Increasing the size of a hydraulic turbine for the hydraulic power generation may result in the decreased rotation power of the hydraulic turbine caused by the resistance of the wind when blades on the hydraulic turbine come out of the water. A blade rotation system on the blades of the hydraulic turbine is provided so that the blades may rotate according to the direction of the wind. As a result, wind resistance is not effected to the rotation of the hydraulic turbine even when the blades on the hydraulic turbine are out of water, but enhances the rotation power of the hydraulic turbine, which enables the use of wind power and hydraulic power at the same time.