Objective To explore the effects of α-Al₂O₃ content on the microstructure and mechanical properties of the coating formed on aluminum alloy by the method of micro-arc oxidation with α-Al₂O₃ addition in electrolyte system. Methods Different ceramic coatings were obtained by adding 1 ~ 5 g / L nanoα-Al₂O₃ additive into the silicate system solution and the micro-structure, thickness, hardness and corrosion resistance were analyzed. Results The main phases of the coating were α-Al₂O₃ , γ-Al₂O₃ and SiO₂ . There were few micro-cracks and small porosity of the coating when the content of nano α-Al₂O₃ was 3 g / L, and the thickness reached 70 μm, the hardness was 513 HV and the corrosion resistance of the coating was good. Conclusion Addition of α-Al₂O₃ into the silicate electrolyte system could improve the comprehensive performances of the micro-arc oxidation coating on alu