Water curtain efficiency test is the key method to evaluate the tightness and reliability of water curtain system. This thesis taking the cavern in Yantai as an example, based on the data of three different hydrodynamic condition stages during efficiency test, in combination with the important judgment parameter of water curtain efficiency-critical pressure value, the low efficiency of rock area was revealed by analyzing and evaluating the conduction effect of fissure water pressure. In order to improve the efficiency, drilled additional boreholes in low efficiency area. At last, through the test to evaluate efficiency improvement of new drilled boreholes. The test result shows that: the water curtain efficiency test can able to accurately determine the low efficiency area in rock mass, additional boreholes can significantly improve the pressure of low efficiency boreholes and can achieve the tightness requirements of cavern.