Abstract: With the assumption that the rock micro-unit failure obeys the Weibull random distribution, the damage softening statistical constitutive relations are established under the true triaxial confinement state. Then, according to the geometrical conditions of the stress-strain relationship, the theoretical relationship between the constitutive model parameters and the stress-strain curve characteristic parameters during the process of rock softening and deforming is established, which enhances the adaptability of the model. Finally, the rationality of the model is verified by the measured data.