Micro-arc oxidation (MAO) surface treatment is often used to improve specific properties of magnesium alloys, but MAO films tend to produce micropores and microcracks, which deteriorate corrosion resistance of magnesium alloy. In order to improve the service life of magnesium alloy micro-arc oxidation (MAO) film, the latest research progress of MAO process adjustment measures and MAO film post-treatment technology at home and abroad was reviewed, and the research hotspot of MAO composite film at home and abroad in recent years was mainly introduced. Several measures to improve the long-term protection performance of magnesium alloy MAO film by process adjustment were mainly summarized. The adjustment of electrical parameters and power supply type combined with the adjustment of electrolyte composition can improve the corrosion resistance of MAO film. Adding additives into the electrolyte can improve the stability and conductivity of MAO electrolyte. Adding self-sealing hole additives can participate in the film formation to improve the compactness of MAO film. The pores were further sealed by composite process after traditional pore-sealing for MAO film. Furthermore, the research progress of composite coating technology was introduced in detail, including the hydrophobic coatings, electroless plating, diamond-like coating and biological membrane coating. It is emphasized that the composite film not only had high corrosion resistance but also had the prospect of functional application. Super hydrophobic composite film had active corrosion protection effect on magnesium substrate, so it can assist MAO film to improve the surface hydrophobicity. The nickel plating layer was compact and has no micropores, improving the conductivity and corrosion resistance of magnesium MAO film by cross bite with MAO film. MAO coating replaced the metal buffer layer to improve the interface bonding strength between diamond-like coating and matrix. The biological composite coating not only had high corrosion resistance but also had biological activity to promote cell proliferation and differentiation. Finally, based on the research status of MAO process of magnesium alloy, the future development trend of MAO composite film was prospected.