In an effort to finalize the optimal formula, the research work was conducted to probe into the preparation, their microstructures and corrosion resistances of micro-arc oxidation (MAO) coatings under different concentration ratios of electrolytes. Based on uniform formula experimental design, AM60B magnesium alloys underwent micro-arc oxidation treatment in silicate-containing electrolyte solution. The two response indexes, micro-arc oxidation feasibility and formability of micro-arc oxidation coating, were designated to verify if the formula for a certain electrolyte solution involved in the paper had practical application potential and evaluate if the coating made under a certain electrolyte solution formula was acceptable. Eddy current thickness gauge, scanning electron microscope (SEM), X-ray diffraction (XRD), electron-probe micro analyzer(EPMA), spotting test and electrochemical test were employed to characterize the thickness, microstructure, phase composition, element composition and corrosion resistance of the coatings, respectively. The results have shown that where the NaOH concentration in the electrolyte solution was less than10 g/L, complete and evenly-colored MAO coating could be prepared. And where NaOH and KF shared almost the same concentration ratio and the sum of the both approximated Na2SiO3 ratio, namely Na2SiO3 was 19.24 g/L, NaOH 8.80 g/L and KF 11.96 g/L, the coating possessed attribute of small micropore size, less defect and great compactness. At this point, the coating performed the best in corrosion resistance. Compared with the matrix, spotting corrosion resistance of the coating was improved by 39 times and its electrochemical corrosion resistance was improved by 3 magnitudes. The coatings in the paper mainly comprised MgO, Mg2SiO4 and a small amount of MgF2 and MgAl2O4, varying with each other in content. The choice of experimental designing is key to validity of the research results. The concentration of NaOH in electrolyte solution is of crucial importance to the practicability of a certain formula for electrolyte solution. Only when the ratio between Na2SiO3, NaOH and KF is reasonable is it possible to minimize micropore size, reduce micro-crack, improve compactness of coatings, and deposit more excellent phase in coatings. They all come as prerequisite and guarantee to enhanced coating corrosion resistance.