Toppling deformation failure is common in layered rock slope projects. It makes sense to research on toppling failure mechanism in slope stability analysis. On the basis of the relevant research both at home and abroad，three main different failure modes of toppling deformation are analyzed. They are flexural toppling，block toppling and block-flexure toppling. Influential factors of toppling deformation like the geometrical shape of slopes， rock strength and the ratio of length to thickness for layers， mechanical parameters of interface, groundwater， excavation effect and so on, are illustrated. Corresponding research methods mainly include physical model tests， limiting equilibrium methods and numerical simulation， with which research headway is presented. Applicability， advantages and disadvantages of those methods when studying toppling failure are pointed out at the same time. Then specific issue to be improved and further studied is proposed.