Based on Mohr criterion,the rock micro-unit strength is redefined.Considering the characteristic that the strength of rock micro-unit is of stochastic distribution,using damage mechanics theory and the statistical strength theory,a damage constitutive model is established under rock triaxial compression test.To form a more general damage constitutive model,the relationship between model parameters and confining pressure is discussed and from which the model parameters are modified.Accordingly,a complete damage constitutive model is established.Contrast with triaxial compression test results,this model can well simulate the relation of stress-strain during the full process of rock failure under the various levels of confining pressure,especially the characteristic of strain softening.Besides,this model is simple and convenient to apply,capable of having properties approaching the actual situation of engineering projects.