Abstract: Slag dump is a common man-made disaster body. Its stability is related to the road traffic in the region. The potential geological disasters caused by the slag dump also have a great harm to the people's production and life in the downstream areas. Based on the engineering practice of an abandoned slag yard along the Xuyong-Dacunzheng Railway, the accumulation process of the abandoned slag is reproduced by the physical simulation method, and the grading characteristics of the slag particle size and the slope structure characteristics of the abandoned slag deposit are studied. Based on the experimental results of the physical simulation and PFC discrete element numerical simulation, the deformation and instability process of the slope of the abandoned slag yard considering particle size classification is examined. The physical simulation results show that the formation of the waste slag deposits is a dynamic process. Under the interaction of gravity and particles, the size of the deposits is highly graded and uneven. From top to bottom, the average particle size increases, the density decreases and the void fraction increases. The discrete element PFC simulation study of the deformation and failure process of slope in the typical abandoned slag yard shows the stages of the back edge down fault, front bulging, potential slip surface formation and slip surface penetration.