Abstract: The influence of the intermediate principal stress on the bearing capacity for a rectangular and metallic cantilever beam was analyzed using the explicit finite difference method and twin shear unified strength theory. The distribution of plastic strain for a cantilever beam under the limit load state is near two symmetry triangles. The influence of the intermediate principal stress on the bearing capacity of a metallic cantilever beam is related to the beam thickness. The influence of the intermediate principal stress on a plane stress beam is lower than that of a plane strain beam. The influence of the intermediate principal stress on the bearing capacity of a plane strain beam is independent of the beam length. The influence of the intermediate principal stress on the bearing capacity of a plane stress beam is increased firstly and decreased secondly with the beam length increased.