Abstract: Combined with micro-arc oxidation (MAO) and dip coating, MAO/PLA/ZnO composite coating was successfully prepared on the surface of AZ31 magnesium alloy.The structure and morphology of the composite coating were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR)and scanning electron microscope(SEM). The corrosion resistance of the composite coating in simulated body fluid (SBF) was tested, and the antibacterial properties of the coating were studied.The results show that the organic-inorganic coating composed of polylactic acid(PLA)and zinc oxide (ZnO) nanoparticles improves the surface structure of the MAO film. The composite coating effectively improves the corrosion resistance of the magnesium alloy, and the corrosion current density is at least 10⁴ times lower than that of the substrate. At the same time, the addition of ZnO nanoparticles makes the composite coating exhibit good antibacterial properties.