This paper proposes a numerical model of the fatigue damage process in short fiber-reinforced plastics. In the fatigue fracture of these composites, the microcracks in the polymer matrix increase with fatigue cycles and dominate the fatigue damage process. Therefore the matrix crack was modeled by the continuum damage mechanics approach while considering the microscopic fatigue damage process in the polymer matrix based on a Kachanov-type damage-evolution law. We applied the model to addressing the fatigue-cycle experiments of short glass-fiber reinforced polycarbonate conducted by Ha et al. The simulated results agreed well with the experimental results. Moreover, the simulation revealed that the dependence of the damage accumulation on the fiber orientation remarkably changes the fatigue life of the short glass-fiber reinforced plastics. © 2009 Elsevier Ltd. All rights reserved.