Porous ceramic coating were prepared on AZ91 magnesium alloy by micro-arc oxidation (MAO), and the duplex coating were prepared by magnetic sputtering copper. The surface phase?composition, surface roughness, surface and cross-sectional morphology, surface wettability, and electrochemical characteristics of MAO and duplex coatings were studied. The results indicate that the surface of AZ91 magnesium alloy treated by MAO shows hydrophilic due to its micro-nano coarse porous structure, and its phase?consists of MgO, Mg and Mg2SiO4. However, the surface of MAO coating turns into relatively compact copper with hydrophobic property after magnetic sputtering copper, at the same time the surface roughness decreases a little. Four-point probe measurement indicates that the duplex coating exhibits well electrical conductivity,the sheet resistance is 16.2mΩ?□-1. Meanwhile, potentiodynamic polarization curves reveal that the corrosion current density of duplex coating reduces to 10%, and the corrosion?potential increases 0.36V, while the polarization resistance increases around 80?times compared with bare magnesium alloy. Compared with the MAO coating, the corrosion?potential of the duplex coating increases 0.24V, suggesting that the corrosion trend decreases. Nevertheless, the corrosion current density and polarization resistance of the duplex coating all decrease to some extent. These?survey?results?indicate that the duplex treatment by MAO and magnetic sputtering copper on surface of the magnesium alloy improve its electrical conductivity greatly?without?losing corrosion resistance of magnesium alloy.