Abstract: Considering the original defect and imperfection buckling characteristics for side slope with bedding rock mass, the post-buckling behavior of defect structure is studied by using the initial post-buckling theory and the cusp catastrophic model, which derives a region near the bifurcation point expressed by the load and displacement. The criteria for buckling failure and shearing slip of rock mass bedding slope are proposed, and an application example of Bawang Mountain slope located in the lower reaches of Yalu River is given. The results indicate that the zero order remainder expressing the original defect in the potential energy incremental function has determined the relation with the ripping factor in the cusp catastrophic model. The critical value at bifurcation point of the side slope with bedding rock mass is determined by its bifurcation set. The critical values of the real significant buckling failure and shearing slip can be obtained only if considering the actual defect for the side slope with bedding rock mass.