The influences of the different content of Rare earth La on the corrosion resistance of AZ81 in the simulated human fluid were studied. In order to further improve the corrosion resistance, different heat treatment procedures were studied. Results showed that with the increase of content of rare earth La, the grain size was refined and the corrosion resistance increased. The corrosion resistance was improved after T6 heat treatment (solid solution+ aging). Microstructure analysis showed that β-phases were precipitated in the T6 heat treatment process. Those fine β phases acted as corrosion barrier and impeded the corrosion extending.