Abstract: The underground plant aera buildings of Lubuge hydropower Project in the karst rocks, the basic elevation of the plant is lower than the water surface of river and the reservoir of lower reaches. Therefore, it is a main problem that prevent the water of the river and another reservoir from leaking to the underground plant. This article introduced a successful example that analysied the regularity of karst developed、the geological structure of rocks and the possible leakage path, and that advanced prevent from leakage prevention design project and processing measures, and that after the processing confirmed achieve good results of leakage prevention in the communicating test and water storage test of the reservoir .It provides for reference on the other similar project.