To study the influence of microstructure of magnesium alloys on preparation of phytic acid conversion coatings, the phytic acid coatings were prepared on AZ91D,AZ61,ZK60,ZM21 magnesium alloys in phytic acid aqueous solution by immersion method, and pure magnesium were used to compare. The surface morphologies of conversion coating were observed, and surface element compositions and concentration distribution of conversion coating were analyzed, and the effect of the microstructure on preparation of phytic acid conversion coating was studied. The results show that alloying elements play a definitive role in forming conversion coatings. Tetravalent and trivalent alloying elements are more helpful than divalent alloying elements. Alloying elements dissolved in the magnesium matrix(alpha-phase)are more beneficial for forming coatings than that in the second-p hase.