Abstract: In engineering projects of landfills,geomembranes were commonly used to isolate waste from the surrounding ground and groundwater in order to minimize the potential groundwater contamination.Subsequent construction of a landfill included the placement of waste layers and soil covers at various heights over the liners.Substantial down-slope shear stresses might be resulted in the geomembranes,leading to the development of significant geomembrane tension which was necessary to be studied so as to ensure the safe use.The relationship between shear stress and displacement for interface between the geomembranes and the clay was divided into three states: elastic,softening and residual strength.Three-state elasto-plastic model was presented to simulate the shear deformation property for the interface,and the governing differential equations of three states were obtained.Because the demarcation points among the three states were unknown,the iterative computation method should be used to compute the tension of geomembranes.Finally,some important factors,including the influence of landfill height and slope gradient on the tension of geomembranes,were studied.