Abstract: To reduce the grid photovoltaic(PV) power fluctuations caused by light intensity and temperature change, based on grid connected power data of a 40 MWp PV power station, the largest active power variation on minute/10 minutes levels is analyzed and its probability is counted. As to the grid connected requirement for PV power fluctuations, the problems of grid connected PV power fluctuations is improved by using of battery energy storage system(BESS) that can store and release photovoltaic power, and the power and capacity requirements of the battery energy storage system are analyzed. In the end, a control strategy which can reduce PV grid power fluctuations by battery energy storage system is proposed, and the simulation results verify the feasibility of control strategy and control algorithm.