Combined with a large scale underground petroleum storage caverns Engineering,the paper took discrete element method and applied UDEC software to simulate the effect of different conditions and dip fractured rocks on seepage field .It also analyzed the effect of water seal in different seepage field conditions. The results shows that the fracture pressure surround cavern will increase with the increase of angle. From 20 to 40 degrees, the fissure water pressure increases quickly,but from 40 to 70 degrees, the fissure water pressure increases slowly.The effect of water seal in the fractured rock cavern of small angle is worse than that of fractured rock cavern with large angle.In order to maintain the water seal effect equally with the former, it is necessary to increase waterhead in the water curtain cave ,but the water inflow in the fractured rock cavern with small angle is less than that with large angle.