Immersion test, electrochemistry test and block-on-cylinder type wear test have been applied to study the corrosion and wear resistance of AZ91D Mg alloy with and without microarc oxidation (MAO) treatment in Hank's solution. Through MAO, a ceramic coating is directly formed on the surface of AZ91D Mg alloy, by which its corrosion and wear resistances are greatly improved. The immersion test results show the mass loss of untreated AZ91D Mg is 15 times of that of MAO ones after 21 days immersion test. The electrochemical corrosion experiments show that the corrosion potential of Mg alloy is improved from -1.5786 V to -0.43019 V through MAO surface treatment, the corrosion current is reduced from 0.028703 A/cm(2) to 2.0456 x 10(-7) A/cm(2), and the polarization resistance is improved from 1.2753x 10(-5) Omega/cm(2) to 0.90886 Omega/cm(2). The lubricate sliding wear test results show the mass loss of untreated AZ91D Mg is 1.5 times of that of MAO ones.