Abstract: The microstructures and hardnesses of Al₂O₃/Cu powders prepared by different oxygen coefficients have been researched. The results show that the reverse diffusion of the aluminum atom is significant at low oxygen coefficient, and the reverse diffusion of the aluminum atom is effectively controlled at high oxygen coefficient. Compared with the oxygen coefficients of 0.6X and X, when the oxygen coefficient is 1.5X, aluminum atom is uniformly distributed in the Al₂O₃/Cu powder, and the Al₂O₃/Cu powder has the highest average microhardness.