Damage is an important mean for the analysis of the deformation and fracture of rock, and statistical damage theory have received much attention in the study of rock damage. Initial damage coefficient, reflecting the inhomogeneous and non-linear of the rock to a certain degree, was proposed by analyzing the shortage of the statistical constitutive model of rock damage. By considering characteristic parameter and geometric condition of rock complete stress strain curve, the difficulties of calculating the parameter of constitutive equation in the traditional method was overcomed, and the calculational precision was improved. At last, based on the triaxial compressive test results of sand rock from a practical engineering, the statistical constitutive model of rock damage was confirmed, and the size-up of q was discussed.
