Uniaxial and triaxial compression mechanical tests were carried out to study the mechanical properties and constitutive relation of rock in post peak state. Based on the different stages and different failure types of rock in the uniaxial and triaxial compression mechanical tests，“segmentation constitutive model” and “damage softening statistic model in different failure types” were built. Yield point，peak point and residual strength point were used to divide the process into three stages in segmentation constitutive model，and the function of constitutive relation was founded. The failure types of rock in compression were divided into tensile failure in low confining pressure，shear failure in high confining pressure，and tensile-shear composite failure in moderate or low confining pressure in the damage softening statistic mode in different failure type，circumferential strain，shear strain and volumetric strain were chosen as damage variables to provide constitutive models，which were proved to be better in describing the relation of stress and strain of rock in the pre-peak and post-peak states，and revealing the damage development process of rock.