Abstract: In order to understand the role of the water curtain system in the storage security of underground cavern, and verify the necessity of setting up the water curtain system, on the basis of an underground water-sealed cavern in Yantai, several simulating conditions are designed, including a no-water curtain system, a single horizontal water curtain system and a horizontal and vertical water curtain system, using the TMVOC module of TOUGH2 software to simulate the three-phase flow of gas, oil and water with multiphase flow theory. The results of numerical simulations indicate that the pollution halos will form round the caverns, in which the horizontal extension is more obvious. As time goes on, the pollution halos between the adjacent caverns pass through each other. Without the water curtain system, the horizontal migration extension of the pollution halos reaches the risk threshold in 9 months. While under the other simulating conditions, the pollution halos have not reached the risk threshold after 100 years of storage, all of which are trapped in a certain range. Besides, the vertical curtain system can markedly inhibit the horizontal migration of the pollution halos. In conclusion, we note that the propane in the cavern leaks easily depending only on the natural groundwater recharge. It is necessary and effective to set the water curtain system to constrain migration of pollution halos and ensure the storage safety of the underground water-sealed cavern.