Abstract: For better modelling the microscopic characteristics and evolution of materials under hydro-mechanical coupling conditions, a TOUGHREACT-based hydro-mechanical-damage coupled numerical model for saturated rocks is established by using the microscopic homogenization method and the thermodynamics theory. The proposed model well accounts for the influences of sliding dilatancy, damage propagation and normal compression of arbitrary microcracks on the macroscopic deformation and failure characteristics, permeability evolution and fluid flow process. The numerical method is successfully validated through the experimental data of water injection tests on coal sample at the laboratory scale and then used to carry out application simulations of water injection responses at the field scale. The numerical simulation results demonstrate that the distributions of injection-induced rock damage and elevated pressure are affected by the injection rate, in-situ stresses and anisotropic distribution of the initial microcracks, and they are more developed in the directions with larger in-situ stress and dominant development of microcracks. Better simulations of the macroscopic hydro-mechanical responses of rocks depend on the accurate characterization of the internal microscopic structures. The research may provide a useful reference for deepening the study on hydro-mechanical coupling of rocks.