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 the cushion layer for actually predicting the stress and deformation behavior of the face slab. At present, the simple shear tests and discrete element simulation investigations related to the contact face between the zigzag extrusion wall and the cushion layer are not available. Therefore, taking a 200 m-level dam as a reference, the large-scale simple shear tests of the contact surface between the extrusion wall and the cushion layer materials are carried out, and the mechanical properties of contact surfaces with zigzag and planar extrusion walls are compared and analyzed. The shear deformation and rotation characteristics and influencing factors of the cushion layer materials are analyzed by using the discrete element numerical simple shear tests for the first time. Compared with the planar extrusion wall, the zigzag extrusion wall causes the larger rotation magnitude of the blocks in the cushion materials and the larger deformation of the cushion materials near the contact surface. Based on the simple shear test results of the zigzag extrusion wall-cushion material contact surface, the contact surface model and the parameters are determined. It is helpful to improve the accuracy of stress and deformation calculation for face slab of high concrete face rockfill dams.