Oxidation behavior of zirconium hydride in O2 at 450-600 °C was investigated by an isothermal oxidation experiment. The influences of temperature and oxidation time on the growth of the oxide film were studied. Results show that a parabolic law is observed in oxidation kinetics for zirconium hydride oxidation in O2 at 450-600 °C. The curves of square thickness (D2) of the oxide film with annealing time (t) follow the linear law. The oxidation progress of zirconium hydride is controlled by inward diffusion of oxygen atoms. The relationship of diffusion coefficient and temperature is represented as Arrhenius Law. The diffusion active energy of the oxidation reaction in O2 is 18724.5 J/mol, indicating a grain boundary diffusion mechanism.