Abstract:A series of formulas about two-parameter parabolic Mohr strength criterion are derived. Based on the results of uniaxial tension test and uniaxial compression test,the parameters involved in the criterion can be determined,and the damage pattern is also discussed. After that,the formulas about the rupture angle and the friction angle are presented,and the formula of their relationship is also presented. Two-parameter parabolic Mohr strength criterion can describe both shear failure mode and tensile failure mode. In this criterion,the ratio of the uniaxial compression strength and the uniaxial tension strength can be set any value. The formulas of the rupture angle provide concrete theoretical foundation for the direction of crack face and damage pattern in the computation of macro crack propagation. At last,it is also pointed out that Griffith criterion is only an exceptional case of two-parameter parabolic Mohr strength criterion.