Abstract: Based on pair functional potentials and Cauchy-Born rule, spring-buddle components and cubage component were abstracted. Integrating the mechanical responses of the two kinds of components, the paper derived the corresponding elasto-damage constitutive relation. Recognizing that the slip is the main plastic deformation mechanism, the paper proposed slip components to describe the plastic deformation, and then derived the corresponding plastic constitutive relation. Based on the decomposition of deformations, the elasto-plastic damage constitutive relation described by three kinds of components was derived. The numerical iteration algorithm under given strain was presented. The calibration of model parameters was illustrated through a tensile numerical case. Simulation of mortar under hydrostatic compression was performed. It is explained from the point of the mesoscopic deformation that the bearing capacity increases as the hydrostatic pressure increases. The numerical results agree well with experimental data, which demonstrates that this model has the capability to deal with nonproportional loading preliminarily.