The paper is about the surface modification of AI alloy for rapid tooling by Micro-are Oxidation (MAO) technology.According to the special demand of mould Used in metal mold casting,thermal fatigue of MAO Coating,and influence of MAO coating on filling capacity of molten metal have been studied.The conclusions obtained are:MAO coating coated on the surfaces of mold is favorable to mold-filling of molten metal and as the coating gets thicker,the flowing capability of molten metal becomes better.The thermal fatigue tests indicated that the thermal fatigue life ofMAO coating is much longer than that of other coatings.