Magnesium and its alloys possess good biocompatibility and mechanical property as absorbable biomedical metals. Their elastic modulus (45 GPa) is very close to that of the bone. However, the disadvantage of the alloys is the rapid degradation rate which can not satisfy the clinical applications. Surface modification is one of the choices for an improvement in the corrosion resistance of magnesium alloys. Chemical conversion is very convenient, effective, and low-cost. According to the reports, small bioorganic molecules such as amino acids can be applied to coat the surface of magnesium alloys with enhanced corrosion resistance and adhesion strength due to molecular recognition, spatial match, and electrostatic adsorption. Amino acids existing in the human body play a critical role in the biomineralization of degradable magnesium-based implants dependent on their molecular structures, type and length of chains, and isoelectric points (pI). Nevertheless, the material-bio-chemical interaction mechanism has not been understood yet.