Abstract: The Qingkou landslide in Wulong, Chongqing, has developed on an inclined thick abrupt cliff, with a large area of goaf formed due to hundreds of years of coal mining below. Based on the analysis of the geological conditions, current goaf situation, and deformation characteristics of the mountain, it is identified that the landslide exhibits both bending-tension and sideslip deformations, suggesting a bending-sideslip failure mode. The deformation history of the mountain is examined, and the deformation characteristics of the landslide are analyzed in two stages: bending deformation and sideslipping deformation. Change in the rock surface occurrence are studied accordingly. Considering the combination relationship between bedding and the free face, the mountain failure is divided into bending-tension failure, wedge failure and plane-sliding failure. Criteria for each failure stage are established, revealing the evolution rules and formation mechanism of the bending-sideslip landslide. This study provides a scientific basis for the disaster prevention and mitigation of such landslides.