Toppling type collapse is one of the majormodels of collapse disasters and usually occurs in the slope with weak layer in the lower part of the hard rock. When the weak layer in the lower part of the slope is affected by the external environment and human engineering activities, tensional cracks will occur and the slope incline outward. There are different failure modes in the topping process because of the diversity of geological structures, and toppling-sliding failure is a common mode of toppling type collapses. According to the stress-strain relation of rock, collapse body can be seen as a rigid body. This paper presents the warning model of fracture width with respect to the consistence of the upper and lower rotation angles of rigid body. Moreover, this warning model has been validated by the two-dimensional and three-dimensional numerical models, and the results of the warning model are between the upper and lower measuring values. It can be concluded that the curve shapes of rotation angles of model are consistent with the variation of the rotation angles of collapse body.