The work aims to improve corrosion resistance and bioactivity of AZ31 magnesium alloy. Micro-arc oxidation films were prepared on the surface of AZ31 magnesium alloy in one piece of electrolyte taking sodium hexametaphosphate as main salt, and the other taking sodium hexametaphosphate as main salt and nano-hydroxyapatite (HA) as additive. Microstructure, element characteristics and phase composition of the coatings were characterized with scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometer (XRD). Corrosion resistance of the coatings was investigated in electrochemical method and by performing immersion experiment. Cell compatibility of the two coatings was evaluated by cell experiment. HA in the electrolyte could enter into the micro-arc oxidation film. Compared with the HA-free micro-arc oxidation film, the micro-arc oxidation film containing HA was more compact and was subject to hole sealing. Electrochemical method and soak test showed that HA-MAO exhibited better corrosion resistance. Cell surface adhesion experiment and cell proliferation experiment showed that AZ31 magnesium alloy receiving HA micro-arc oxidation not only had better biocompatibility, but also promoted proliferation of MC3T3-E1 cells. Addition of nano-HA in the sodium hexametaphosphate solution can produce HA-containing micro-arc oxidation coating on the surface of AZ31 magnesium alloy, and its corrosion resistance and bioactivity are superior to those of HA-free micro-arc oxidation coating.