A kinetic model predicting the oxidation of carbon fiber reinforced glass matrix composites has been described. The weight loss of composites during oxidation implied that a gasification of carbon fiber takes place and the transport of reactants $(O_2)$ or product (CO or $CO_3$) in the glass matrix was partially the rate controlling step. The kinetic model in this study was based on the work of Sohn and Szekely which may be regarded as a generalization of numerous models in the gas-solid reaction system. A comparison of this model with experimental data is also presented.