Abstract: In order to ensure smooth running and battery capacity optimization of hydrogen production by wind-solar complementary system,an improved determination method of battery capacity is proposed in this paper,with subsequent implementation in combination with the single power,dual power and triple power modes of hydrogen production unit. The following factors are taken into consideration:average power of hydrogen production,required capacity of the battery,hydrogen production power switching and working power fluctuation. Results show that the dual power scheme can reduce the capacity of the battery to a large extent,and the difference between high and low power is within the allowable range,making the power switching simple and easy to be operated.