Due to the spontaneous degradability, excellent biocompatibility, favorable bone−inducibility, and antimicrobial properties, Mg−based alloys acting as miniature intravascular stents and bone−fixation materials have shown great development−potential. Regrettably, the uneven degradation model and excessive dissolution rate restricted their clinical application. In this study, the latest research on five methods (high−purity or amorphous, micro−alloying, heat−treatment, plastic−deformation, and surface modification) in medical Mg alloy degradation behaviors was reviewed. The corrosion mechanisms of Mg alloys under different processes were summarized. In addition, the effects of microstructure characteristics and film−layer features on corrosion resistance were systematically discussed. Ultimately, existing problems and future development directions of medical Mg−based alloys were reviewed.