A coating was prepared on zirconium by micro-arc oxidation. The effects of voltage, frequency, duty-cycle and current density on the thickness of the MAO coating were studied, and the significances of the effects were also studied by ANOVA. The results show that the thickness of the coating increases with the voltage, duty-cycle and current density increasing and the frequency decreasing separately, the primary-secondary order of the effect significances for all parameters is voltage and current density > duty-cycle > frequency, and the frequency has little effect on the coating thickness.