Graphene oxide (GO) was added into the electrolyte during the preparation of the pla**a electrolyticoxidation (PEO) coating on AZ31 magnesium alloy. The effects of the GO additive on the microstructure,phase composition, and corrosion resistance of the PEO coating were studied. The results demonstratedthat GO successfully incorporated into the PEO coating and it was partially reduced to rGO during the PEOprocess. As a result, the number of micropores on the PEO coating was significantly decreased. Moreover,the electrochemical test revealed that the corrosion resistance of the PEO coating was markedly improvedupon the incorporation of 2 g/L GO.