Selective growth of oxidation coating was observed on Mg matrix composite Al_(18)B_4O_(33w)/AZ91(a composite with Al_(18)B_4O_(33) crystal whisker as reinforced phase) when this composite was treated by microarc oxidation (MAO) technique,and then the role of Al_(18)B_4O_(33) whisker in the process of MAO was analyzed.The protective properties of MAO coating also were investigated.Scanning electron microscopy(SEM) was used to characterize the existing state of Al_(18)B_4O_(33) whisker in MAO process and the microstructure of MAO coating.Corrosion resistance of the bare and coated composite was evaluated by immersion corrosion test and potentiodynamic polarizing test.Wear resistance of MAO coating was investigated by a ball-on-disc friction and wear tester.The results showed that sparking discharge did not occur on Al_(18)B_4O_(33) whisker and the whisker existed in the coating as a heterogeneous phase when MAO coating grew on the composite;then the whisker would be covered gradually with growing thick of the coating.Corrosion current density of the coated composite was decreased by 4 orders of magnitude compared with that of the uncoated composite; excellent corrosion resistance was closely related to the compact whisker-coating interface since Al_(18)B_4O_(33) whisker did not induce structural defects.The coating also exhibited high wear resistance and a slight adhesive wear tendency with bearing steel as its counterpart material. Selective growth of oxidation coating was observed on Mg matrix composite Al_ (18) B_4O_ (33w) / AZ91 (a composite with Al_ (18) B_4O_ (33) crystal whisker as reinforced phase) technique, and then the role of Al_ (18) B_4O_ (33) whisker in the process of MAO was analyzed. The protective properties of MAO coating also were investigated. Scanning electron microscopy (SEM) was used to characterize the existing state of Al_ 18) B_4O_ (33) whisker in MAO process and the microstructure of MAO coating. Corrosion resistance of the bare and coated composite was evaluated by immersion corrosion test and potentiodynamic polarizing test. Wear resistance of MAO coating was investigated by a ball-on-disc friction and wear tester. The results showed that sparking discharge did not occur on Al_ (18) B_4O_ (33) whisker and the whisker existed in the coating as a heterogeneous phase when the whisker would be covered. wit h growing thick of the coating. Corrosion current density of the coated composite was decreased by 4 orders of magnitude compared with that of the uncoated composite; excellent corrosion resistance was closely related to the compact whisker-coating interface since Al 18 B 4 O 33 whisker did not induce structural defects. coating also exhibited high wear resistance and a slight adhesive wear tendency with bearing steel as its counterpart material.