The damage evolution about the fiber- cement matrix composites is evaluated by considering the damage evolution of the matrix concrete and that of the fiber- matrix interface. The damage evolution of interface is explicated by the relationship of interface debonding and the fiber displacement. Based on the FEM, considering the effect of the interface layer and that of fiber- matrix mixing, the relationship between load and interface crack length and that between load and fiber displacement are obtained when different elastic module and interface layer thicknesses are given. The model is very useful to analyse the damage evolution of composites.