In order to improve the dynamic characteristics for largeflow pilotoperated check valve, the flow field of largeflow pilotoperated check valve was analyzed using fluid dynamics analysis method. The variation instance of pressure and liquid phase was investigated in operation of the largeimpactflow valve. At last, the dynamic characteristics and power spectrum of largeflow pilotoperated check valve were analyzed by experiments. The results indicate that in reverse opening of the check valve, the greater the flowarea is, the shorter the unloading time, and the faster the flow rise, and the lower the cavitation index are. But the flow capacity is strongest when flowarea is of 312 mm2, and the rule of pressure fluctuation is not a linear decreasing.