Abstract: An increase in the number of rock slope instability case that was characterized with "toppling" movement was found in the practice of engineering geology in west China in the past decade. The significance of the potential threats caused by toppling failure has arguably moved abreast of that induced by the conventional slope movement type commonly known as "sliding", and thus it has become a more pronounced challenge faced by engineering geologists and geotechnical engineers. The critical issue in the study of toppling failure is that the current analytical and/or empirical models are primarily based on the hypothetical slide of rock slopes without considering other forms of movement. The paper analyzes the deformation and failure process of toppling movement in light of the field data obtained from a large number of engineering projects. The study of toppling movement presented here constructed engineering geology models to depict the deformation at various stages and divided the movement into the types of toppling-falling, toppling-slipping, toppling-cracking, and toppling-loosening, which provides systematic qualitative descriptions and quantitative thresholds for the characteristics of each movement type. The study aims at unifying the understanding of geological significance, static and dynamic mechanics, and slope stability analysis to provide means of evaluating the stability of rock slopes prone to toppling failure. The slope stability evaluating criteria are primarily based on deformation process compare to the previous criteria utilizing strength to assess the stability of slope subject to sliding movement.