Abstract: Surface alloying treatment was conducted by vacuum thermal diffusion aluminized on AZ31 magnesium alloy.The microstructure,phase structure, corrosion resistance and micro-hardness of the aluminized layer by different parameters were analyzed and studied.The electrochemical corrosion polarization curves of the alloy were measured before and after being aluminized for 4 h at 400℃.Test results show that aluminized layer is mainly composed of Mg₁₇Al₁₂, Mg₃Al₂ and α-Mg. The thickness of diffusion layer increases with the diffusion temperature. After diffusion aluminizing treatment at 400℃ for 4 h, a continuous and fine aluminized layer, on the surface of the matrix was obtasneel obtained the micro-hardness value increased from HV 53 to HV 80-85 of the base metal. At the same time, the method enables the corrosion potential of magnesium alloys to increase about 105mV, and the corrosion current density to reduce one order of magnitude, which characterized of the magnesium alloy corrosion resistance is improved.