Abstract: Xiangshuping landslide is located at the Qixin couple of Daping county in Dejiang county, Tongren prefecture, Guizhou province. It is a large ancient landslide. There are several pull trap slots in the boundary of the landslide and the front of the lower slope. Sliding direction of the landslide is 310～335.On the basis of the Engineering geological conditions and deformation and failure characteristics of landslide area, this paper builds the conceptual model of the formation mechanism. In the valley formation and evolution, Xiangshuping landslide evolves in the forms of sliding and bending. The pull slot LC6# and pull slot LC3# in front of the slope are sequentially formed. Their unloading and overhead effects lead to further deformation in upper slope and causes stress concentration at the base of slope and drop of overall slope stability. Landslide occurs while the base of slope is unstable. Numerical analysis well reproduces the landslide evolution and mechanism. The result of the research can provide reference for analogous landslide developmental conditions and identifications of the western mountains.