The paper studied the water supplement control of sealed petroleum cavern is.According to the criteria of vertical hydraulic gradient,it gave the minimum overpressure of petroleum cavern when it operates safely.By monitoring the water pressure around caverns due to setting artificial water curtain,it calculated the vertical hydraulic gradient around the caverns under condition of different heights of the water table and different heights of water curtain tunnel so as to find out the minimum water curtain overpressure during the safe run of cavem,and studied the effect of water curtain design parameters on the minimum exceed pressure of the water curtain.The results were applied to some water sealed underground petroleum storage project. The results show that when the distance from groundwater level to top of cavern is less than 70m,it is necessary to design different curtains of overpressure according to the height and space of water curtain tunnels.The results can provide an important basis for the safe operation of petroleum caverns.