ABSTRACT: In order to research the mechanism of large-scale deep-seated landslide movement at the edge of loess tableland in Weihe River basin, this paper confirms the characteristics of geometry and kinematics of deep-seated landslide and preliminarily reveals the sliding-control mechanism for plastic flow extrusion of clay rock slip band through analysis on the tectono-geomorphologic process of slope on the north bank, balance computation of geological section of landslide mass and dynamic numerical simulation of movement process and in combination with research on the macromechanics background, characteristics of physical structure changes and characteristics of shear creep and sliding mechanics of clay rock slip band development. The research indicates that: (1) The deformation of large-scale deep-seated landslide movement transfers from the trailing edge to the foot of slope. The trailing edge descends and front edge rises. The overall deformation is controlled by mudstone at the bottom with horizontal displacement to a certain extent. It is of rotatory-translational revived landslide; (2) The clay rock slip band develops to be a creep deformation band due to tectonic damage. During landslide, the plastic deformation zone below the sliding mass presents a diagonal triangle. It takes reverse overthrust movement to form the overturned structure and it presents plastic flow deformation and flow extrusion damages; (3) The plastic flow deformation of clay rock is caused by increase of clay mineral content and activity enhancement. The clay content (<2μm) within the slip soil is increased to 50.22% from the original 17.94% while the absolute content of montmorillonite is increased to 26.38% from the original 13.19%. The specific surface area of clay rock is increased to 215.08 from 124.55 on average, which could easily lower the strength of clay rock, deteriorate water-physical properties and give rise to severe deformation of the sliding mass. And the high pore water pressure occurred in the sliding mass could push the sliding mass to move.