Abstract: A comprehensive study has been done of the stability of geomembranes anti seepage system by both centrifugal model testing and limit equilibrium analysis. The innovation of the anti seepage system is in that the conventional stone cushion overlying on the geomembranes is tried to be substituted by a layer of compacted fill. The factor experiment method is used in the model tests to determine the influence of types of geomembranes, angle of upstream slope, and thickness of ovevlying cushion of compacted fill. Moreover, equations of the factor of safety of geomembranes anti seepage system are given for the most critical conditions and justified by the results of model tests. The successful practical example is also presented in the paper to encourage such substitution in the light of local conditions in the application of geomembranes in practical engineering.