A micromechanics-based elastic-damage model considering cumulative damage is proposed to predict the effective stress-strain response and damage evolution in particulate composites. A cumulative damage model combining the Weibull probability distribution function (Weibull, 1951) and the step-stress concept (ReliaSoft, 2003) is incorporated into micromechanical formulations (Ju and Chen, 1994a, b) for more realistic prediction of evolutionary interfacial debonding. A multistep damage process is introduced to model accumulated damage induced by the interfacial debonding. A parametric study of Weibull damage parameters is carried out to examine the sensitivity of the parameters to the proposed model. Finally, present predictions are compared with other numerical predictions and experimental data to assess the predictive capability of the proposed model.