Abstract: A pumped-storage power station has high filling of the upper reservior bottom 120 metres in thickness, and the settlement deformation and local uneven deformation are obvious after water storage. HDPE geomenmbrane is used to get better adaption of the defomation of the reservior bottom to ensure the seepage prevention function. In additon, 3D finite element method is taken to analyze the above problems. For the are as with large local tension strain, engineering measures such as increasing modulus region are adopted. It may provide reference for similar projects.