The Nb2O5 coating was prepared on AZ31 magnesium alloy by DC reactive sputtering technique and the coating was annealed at different temperatures. The microscopic morphology, crystal structure, bonding properties, and corrosion resistance of the Nb2O5 coating were tested and characterized through scanning electron microscope (SEM), X-ray diffractometer (XRD), scratch tester, and electrochemical workstation. The results show that the crystalline phase of the Nb2O5 coating remained unchanged and amorphous at annealing temperatures of 100 ℃ to 400 ℃, while the hexagonal phase appeared at annealing temperatures of 500 ℃. As the annealing temperature increased, the cracking phenomenon on the surface of the coating intensified, the bonding force of the layer decreased, and the corrosion resistance weakened.