Abstract: Tension failure of geomembrane in anchorage zone of surface barrier for high rock-fill dams will be inevitably caused by clamping effect. A set of model tests are performed to verify and analyze the failure properties of geomembrane due to the clamping effect in the anchorage zone of surface barrier using self-developed devices. The test results show that the geomembrane cannot move freely and yield tension failure when differential settlement occurs between dam foundation and cutoff wall or dam surface and rock of bank slope. The excessive friction between the geomembrane and the contacting material is the main reason of tension failure of the geomembrane in small anchorage zone. The traditional anchoring structures including line-shaped anchorage, spirally wrapped anchorage and folded anchorage will all inevitably induce the excessive tension defamation of geomembrane next to their connection to anchorage structure. Under the same differential settlement, PVC geomembrane exhibits a stronger adaptability to the differential deformation compared with to PE and HDPE geomembranes. So the PVC geomembrane should be a preferred selection when used as the surface barrier for high rock-fill dam on thick pervious foundation.