The influences of different oxidation time on surface morphology, thickness, elemental distribution and phase composition of micro-arc oxidation coatings on ZL205A was studied. The results show that with the increase of oxidation time, the number of micro-pores decreases while the size of micro-pores,the thickness increase. The content of Al, Si has little changes, O, P element did not change significantly. The MAO coating are mainly composed of α- Al₂O₃ and Mullite(Al₆Si₂O₁₃), with increasing oxidation time, the content of α- Al₂O₃ and Mullite increased,the Mullite phase mainly generated by the anode reaction product of SiO₂ and Al₂O₃.