Cu₆₄Zr₃₆ metallic glass powders were prepared via gas atomization. The high-temperature oxidation behavior of Cu₆₄Zr₃₆ metallic glass powders under the influence of internal factors (powder particle size) and external factors (oxidation temperature and oxidation time) was experimentally investigated by using XRD, DSC, TGA, SEM and TEM. The oxidation kinetics, oxide phase, surface morphology and microstructure of metallic glass powders were analyzed. The results show that Cu₆₄Zr₃₆ metallic glass powders form multiple layers of surface oxides after oxidation and the major components of the surface oxides are t-ZrO₂, m-ZrO₂, Cu₂O and CuO. The oxidation kinetics follows a double-stage parabolic rate law. The oxidation process is dominated by the inward diffusion of O anions and the outward diffusion of Cu cations. Thermodynamic analysis shows that the Gibbs free energy change of the oxidation reaction increases with the decrease of particle size, leading to a more rapid and thorough oxidation of the powder with a smaller particle size.