Water curtain system is the most critical part of underground water-sealed oil storage, which is composed mainly of water curtain channel, water curtain hole, additional water curtain holes, monitoring well and instrument well. The results of hydraulic test are the basis of the water curtain system apprising and the construction quality of water curtain hole is the guarantee of hydraulic test and the test results. According to the project of an underground water-sealed oil storage cavern in Liaoning, the paper explains the hydrological test method during the water curtain construction, analyzes the function and correlation of each hydrological test during the construction and introduces the construction technology of water curtain hole.