Ceramic coatings were deposited on AZ31B magnesium alloys by constant current micro-arc oxidation (MAO) in 0.333 mol/L (NaPO3)6 +2 g/L NaOH electrolytes with and without the addition of triethanolamine (TEA).The MAO process was discussed by measuring cell voltage-time response.The Cross-section fracture,surface morphology,element composition and thickness of different MAO coatings were studied by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis.The corrosion resistance properties of different MAO coatings were evaluated in 3.5 % NaCl solution with potentiodynamic polarization test.The results indicated that the addition of TEA had not influenced the MAO voltage-time response effectively.With proper concentration addition of TEA,the coating properties such as thickness,surface morphology and corrosion resistance were improved while the coating compositions were not distinctively changed.When the concentration of TEA increased beyond 1 ml/L:The coating thickness was close to the thickness of coatings fabricated when the concentration of TEA was 1mLJL ; The number and size of micro-pores on MAO coatings increased; The corrosion current (lcorr) increased as well as the corrosion potential (Ecor) decreased.