Abstract: The FEM and DEM coupled method (FEM/DEM) can be used to calculate small displacement of continuum, and is also used to simulate the formation of the fracture and calculate big displacement of discontinuum. This study takes the Jianchuandong dangerous rockmass as an example, analyzing the potential failure process of the Jianchuandong dangerous rockmass. The results show that the base of the pillar-shape rockmass is in the stress concentration state, and there are tension and compressive stress concentration zones. Stress concentration can cause the failure of the boundary of the base of the pillar-shape rockmass. Fractures are new-borned by stress concentration, the extension of fracture cause the disintegrate and the final failure of the dangerous rock mass. The FEM/DEM method may pre-produce the formation of the fracture caused by the compressive stress in the pillar-shape dangerous rockmass and the whole dynamic process of the broken mass. The FEM/DEM method can help people analyze the mixture of small and big displacement in the deformation of the slope usefully, which is an important development trend in the future of numerical simulation.