Abstract: Rock mass reverse and fragmentation are an important deformation and failure mechanism. It is of great significance to study the cause mechanism of reverse and fragmentation. Taking the bank slope of upper reservoir of the Ningguo pumped-storage power station in Anhui Province as the research object, the spatial distribution characteristics of reverse and fragmentation were analyzed, and combining with the tectonic stress, the formation mechanisms of tuff bedding-like reverse and rock mass fracture were determined. The investigation results showed that the bedding-like reverse was distributed between the faults F2 and f5. Combined with the plate girder bending theory and the bottom friction simulation tests, the reverse was mainly formed by the traction structure of the faults. As the fault F2 was in a ‘right rotation’ movement, which lead to the tensile stress state of the rock mass in the NW wall of the fault F2, it resulted in the fragmentation of the rock mass. Both the reverse process of the bedding-like and the gravity action in the later stage contributed to the fragmentation of rock mass. The research on the genetic mechanism of tuff reverse and fragmentation in this pumped-storage power station has important references for revealing the engineering geological characteristics of the same type of slope.