High-capacity wind-solar-battery hybrid power system provides a referable generating mode for high permeability intermittent energy connected to grid in the future. Compared with separate photovoltaic or wind power generation, the hybrid wind-solar-battery power generation system can make up the defect of uneven distribution of natural resource based on the complementary characteristics of wind and solar resources. Configuring energy storing device with appropriate capacity to stabilize fluctuation, the output power is managed uniformly by energy management system to realize the wind power and solar energy’s storage and release, and decrease the output power fluctuation. A measurement index is proposed based on improved entropy which is developed in the index of traditional standard deviation. Battery’s charge-discharge power in every moment is scheduled in a cycle to make the output power minimum. A case study is presented to verify that the index of improved entropy’s valley-to-peak is smaller than the situation of simply considering the standard deviation, and the fluctuation is small, so the spinning reserve capacity is reduced.