Slope,which is a natural geological integration,can be divided into two types-soil slope and rock slope.Qualitative analysis and quantitative analysis are often used in the slope stability assessment.DEM used in this paper belongs to quantitative analysis.The traditional approaches to slope stability assessment are hardly to reflect the unstability mode and destruction process.However,DEM owns apparent advantages on the analysis of non-continuum medium's deformation and destruction.Based on the bedding shale slope in debris deposit,the meso-parameters of PFC model was determinated by comparison of meso-parameters in simulated uniaxial compression test and macro mechanics parameters.It shows that the parameters used in the former simulations could be used in the subsequent stability assessment model of slope.Expasion method was used to establish the model in this paper.In this method,balls were generated in specified areas.Then the radius of balls were enlarged until contact forces were generated.Balls were driven to move around for balance and then the areas were filled with balls.A general study on stable state of the slope was carried out using DEM.Sliding process and sliding distance were also studied.The results show that:the completely weathered shale slipped down and deposited at the bottom of the slope.The strong weathered shale and intermediary weathered shale didn't slip.The sliding surface was a interface between completely weathered shale and strong weathered shale.Compression fractures are the primary fractures which only occur on the completely weathered layer.Owning to the small strength of the completely weathered shale layer,most parallel bonds break because of gravity.Grains' spilling out of the bottom makes the middle-upper grains slide downwards on account of lacking supports.Based on the analysis above,cutting slope should be adopted.The simulation results are in agreement with the stereographic method,and it can instruct the design and construction of the project.