Ceramic coatings were prepared by a constant current mode on the surface of 2A12 aluminum alloy, which employed the rare earth cerium dioxide (CeO2) adding to silicate electrolyte. Effects of CeO2 concentration on the morphology, organization, roughness, hardness and corrosion resistance of the micro-arc oxidation ceramic coatings were analyzed using scanning electron microscope, X-ray diffraction, roughness tester, hardness tester and polarization curve, respectively. The results illustrate that surface roughness and pore diameter of the coatings decrease after adding CeO2, while the thickness increases. Most of the CeO2 deposit on coatings in the form of CeO2 compound. A few of CeO2 participate in reaction and generate CeO and CeAl11O8. CeO2 promotes phase transformation from γ-Al2O3 to α-Al2O3; furthermore, the hardness of coatings is improved. When the concentration of CeO2 is in the range of 3 g/L~4 g/L, the corrosion resistance of the coatings is optimal.