The geometrical damage model of rocks is an important basis for the establishment of statistical damage constitutive model. Based on the mechanical properties of rock deformation, the existing geometrical damage models of rock are reviewed and these models have difficulties in considering the initial damage and post peak deformation failure characteristics. The rock mass is composed of the undamaged part, the initial damage part and the subsequent damage part, and a geometrical damage model of rocks considering the initial damage is proposed in this paper. The parametric geometric damage model of rocks is established by studying the influence of Weibull distribution parameters m and F0 on the variation of damage variable. Furthermore, a statistical damage constitutive model of rocks characterized by strain softening is established and modified, and the determination method of model parameters is given. The model verification and parameter analysis show that the modified model can better simulate the whole process of rock deformation and failure. The influences of parameters λ and η on damage variable are equivalent to m and F0, which solves the common problems of current rock geometric damage models. It demonstrates that the model and method in this paper are reasonable and feasible.