Metallic cementation treatment about Al, Zn elements on ZM5 magnesium alloy was conducted by solid diffusion.It was shown that the solid diffusion layer was mainly composed of Mg-Al-Zn intermetallic compounds and Mg-Al-Zn solid solution transition zone that had more Zn and Al elements than standard ZM5 magnesium substrate did. The test indicated that the microhardness values of Mg-Al-Zn intermetallic compounds were much higher than that of the substrate, and this would greatly contribute to the enhancement of wear resistance. The diffusion alloying layer was an effective corrosion barrier to decrease the corrosion rate for ZM5 magnesium alloy when exposed to 3.0% NaCl solutions.