A unified expression describing the nonlinear characteristics of strengths of various materials on the π plane and the meridian plane is used in the generalized nonlinear strength theory. Thus a brand new system of the nonlinear strength theory is formed. The nonlinear strength theory is developed from the single nonlinear strength theory which can be just suitable to a certain material to the generalized nonlinear strength theory which can be suitable to various materials. Therefore

the system of strength theory is completed. The generalized nonlinear strength theory includes a series of the single nonlinear strength theories which have already existed and might appear in the future

such as Mises's criterion

SMP criterion

etc.. The superiority of the system of the generalized nonlinear strength which is suitable to various of materials is verified by the strength tests on clay

rock and concrete.