Abstract: The geological condition of the upper reservoir for Liyang Pumped Storage Power Station is complex. Because the thickness of filled landfill at the bottom of the reservoir varies rapidly and the differential settlement is large, the HDPE geomembrane is adopted as the material of reservoir bottom seepage prevention system owing to its flexibility to unequal transformation, which reduces the seepage loss and make the construction be easier. The design and application of geomembrane seepage prevention system are introduced, including selection and design of materials for seepage prevention layer, surrounding connection design of geomembrane, construction method of geomembrane etc.