MgO-CaO clinker refractory has the disadvantage of poor hydration resistance.MgO coating was deposited on the surface of MgO-CaO clinker by carbothermal reduction of MgO with carbon black as reducing agent and oxidation of the resulted vapor-phase Mg through diffusion.Deposition kinetics，morphology and growth mechanism of MgO coating and influence of coating thickness on hydration resistance of MgO-CaO clinker were investigated.The results indicated that there existed two kinds of controlling mechanism at 1400—1600℃.Deposition process was controlled by chemical reaction and the apparent activated energy was 97.82 kJ·mol-1 at 1400—1500℃.However，at 1500—1600℃ the process was controlled by diffusion，and the apparent activated energy was 19.18 kJ·mol-1.Morphology of MgO coating showed that the MgO growth on magnesia or calcia was typical two-dimensional step-like，but the growth mechanism of MgO coating on either one was not the same.Hydration results showed that the optimal process parameters was that MgO-CaO clinker was treated at 1600℃ for 6 h，and the mass gain percent for treated MgO-CaO clinker was 0.02%，which was 1/150 of untreated one.