This paper develops a mathematical model for fatigue damage evolution in composite materials.The characteristics of damage growth in composite materials are studied and compared with those of damagegrowth in homogeneous materials. Continuum damage mechanics concepts are used to evaluate the degradationof composite materials under cyclic loading. A new damage accumulation model is proposed to capturethe unique characteristics of composite materials. The proposed model is found to be more accurate than existingmodels, both in modelling the rapid damage growth at the early stages of life and near the end of fatiguelife. The parameters of the proposed model are obtained from experimental data. A example is implementedto illustrate that the proposed model is able to accurately fi t several diferent sets of experimental data.