Abstract: The paper takes the slope behind a substation in northern Sichuan as the research object, the characteristics, causes and mechanism of slope deformation and failure are analyzed in detail by integrating the investigation results of geological environment conditions of slope, qualitative analysis of geological process of deformation and failure and numerical simulation results of granular discrete element PFC2D.The results show that the slope is a typical loose accumulation body slope, and excavation unloading is the main control condition of deformation, and heavy rainfall is the main inducing factor of deformation and instability. The deformation of the slope has experienced three stages of evolution: excavation unloading deformation, deformation development extension, and deep creep - potential slip surface penetration. The deformation and failure mechanism of the slope is the creep cracking landslide induced by heavy rainfall under the condition of leading edge excavation. This study can provide a reference for this project and similar loose accumulation slope treatment.