Abstract: The extrusion wall technology has been widely used in high concrete face rockfill dams in the 21th century. It is very important for dam safety to study the mechanical properties of the contact surface between the extrusion wall and cushion layer for actually predicting the stress and deformation behavior of the face slab. At present, the simple shear test and discrete element simulation investigation related to the contact face between the zigzag extrusion wall and cushion layer are zero. Therefore, taking 200m level dam as a reference, the large scale simple shear tests of the contact surface between the extrusion wall and cushion layer material was carried out, and mechanical properties of contact surfaces with zigzag and planar extrusion walls were compared and analyzed. The shear deformation and rotation characteristics and influencing factors of cushion layer materials have been analyzed by discrete element numerical simple shear tests for the first time. Compared with planar extrusion wall, it was found that the zigzag extrusion wall causes the larger rotation magnitude of the blocks in the cushion material and the larger deformation of cushion material near the contact surface. Based on the simple shear test results of the serrated extrusion wall-cushion material contact surface, the contact surface model and the parameters were determined and it is helpful to improve the accuracy of stress and deformation calculation of high concrete face rockfill dam face slab.