Abstract: The shear behaivior of copper waterstop is crucial to its effect in joints of concrete faced rockfill dam On the basis of shearing test, the effects of sizes of each part of the copper waterstop structure to its shear behavior are studied in this paper, using large deformational elastic-plastic FEM A systematic suggestions are offered to the copper waterstop design, which compensates the deficiency of the pure testing research in systematization and depth