A phosphate-permanganate surface treatment with additives Na 2 MoO 4 and NaF was developed to improve the corrosion resistance and bond strength of magnesium AZ31. The phosphate coatings which have the magnesium phosphate, MgO, Mg (OH) 2 , MgF 2 and a minor of Al 2 O 3, Al(OH) 3 Al 0.35−0.55 Si 0.10−0.48 P 0.13−0.35 O 2.1−2.2 and, Al 0.35 S i0.48 P 0.18 O 2.2 , and Al 0.52 P 0.48 O 2.2 were formed on the surface of magnesium AZ31. A combination addition of the Na 2 MoO 4 and NaF in the phosphate solution improves the corrosion resistance and bond strength of phosphated magnesium alloys. The optimal contents of NaF and Na 2 MoO 4 are 0.8g/L and 0.5g/L, respectively.