Abstract: The optical isomerism of the amphoteric α-alanine and Ca²⁺ complexes (S-Ala·Ca²⁺) in water-liquid phase environment is researched by using density functional theory-based M06-2X methods combined with the SMD model method based on self consistent reaction field (SCRF) theory. The study shows that there are three channels a, b and c in the optical isomerism reaction of S-Ala·Ca²⁺. In channel a, the proton transfers to α-C from protonation amino after α-H is transferred to carbonyl oxygen. In channel b, the proton is transferred merely using carbonyl oxygen as a bridge. In channel c, the proton is transferred to carbonyl oxygen from protonation amin and then transfers with amino nitrogen as a bridge. Calculations of potential energy surface shows that the channel c has advantages under the effect of recessive solvent and the inherent energy barrier of the rate-determining step is 232.8 kJ·mol⁻¹; a and b are inferior channels and their inherent energy barrier of the rate-determining step is 268.6 kJ·mol⁻¹. Channel a and b are at a slight advantage with the explicit solvent effect and the inherent energy barrier of the rate-determining step is between 141.3 and 145.0 kJ·mol⁻¹; channel c has a slight disadvantage with the inherent energy barrier of the rate-determining step is between 153.1 and 161.0 kJ·mol⁻¹. The results show that α-alanine Ca (Ⅱ) complex is hard to racemize in water-liquid phase environment. It has good safety to be used for life supplementing calcium and alanine.