Abstract: The formation reasons of accumulation bodies are different, with diverse structures and physical and mechanical properties, which bring about challenges on the stability evaluation of deposits.A slope accumulation body with unknown causes in the lower reservoir area of Lushan Pumped Storage Power Station may pose a threat to the construction safety and long-term operation safety of the hydropower station.In order to ensure the accuracy of the stability evaluation of the accumulation body, based on the detailed field investigation including the UAV tilt photography, LiDAR aerial photography, drilling and other technical means, the accumulation body was investigated, and the formation causes of the accumulation body and the evolution of geomorphology formation were analyzed in-depth.The results show that: ① The main material of the accumulation body originates from the steep cliff on the downstream side of the accumulation body.② The accumulation body contains soft and weak interlayers of varying depths and discontinuities, and it is assumed that the accumulation body is formed by multiple collapses of the downstream cliffs.③ It is speculated that at least two phases of large-scale landslides occurred in the study area, and the present landforms are gradually formed after a long period of surface modification.④ Based on the in-depth argument on the causes of the accumulation body, it is confirmed that the there is a through and weak interface at the base-cover interface of the accumulation body, and the depth of the weak interlayer inside the accumulation body is different and discontinuous.Therefore, the structure and strength of the base-cover interface of the accumulation body should be analyzed as the main influencing factors in exploring the stability of the accumulation body.The results can provide a reference basis for the study on genesis mechanisms of similar complex accumulation bodies.