Magnesium alloys have great application potential and development prospect in the field of medical implants, due to their excellent biosafety, good load-transfer and unique degradation behaviors. However, the corrosion dissolution rate of magnesium alloys was too fast under physiological environment, which leads to accelerated mechanical property decay and premature failure. As an important way to improve the corrosion resistance of magnesium alloys, surface modification can not only slow down the dissolution rate of metal materials through the formation of surface physical barrier, but also inhibit the intensity of corrosion galvanic reaction inside the alloy and regulate its biocompatibility. The technical advantages of typical surface modification processes were summarized, including multi-coverage, high film thickness, strong adhesion and good biocompatibility of coatings on the alloy surface. At the same time, the problems existing in several surface modification processes were summarized, including poor long-term corrosion resistance, low stress tolerance and technical safety. On this basis, the latest research trends of surface modification coatings on magnesium alloys in recent years were reviewed, and the formation mechanisms of several common surface modification coatings such as chemical transformation, micro-arc oxidation and plasma spraying were briefly introduced. The effects of coatings on the degradation process and biocompatibility of magnesium alloys and the mechanism of some elements or particles on the microstructure and biological properties of the coatings were systematically described. Finally, the future development of surface modified coatings on medical magnesium alloys was prospected.