Abstract: A synthesis method of alpha-hydroxycarboxylic acid ester is provided. In the method, an alpha-hydroxycarboxylic acid and an alcohol are taken as raw materials, one or more of boric acid, metaboric acid, pyroboric acid, and boric anhydride is taken as a catalyst, and one of cyclohexane, toluene, benzene, and alcohols is taken as a water-carrying agent. A reaction temperature is kept in range of 100-160° C., produced water is separated by an oil-water separator, and the alpha-hydroxycarboxylic acid ester is synthesized directly. After an esterification reaction, the water-carrying agent and unreacted alcohol are distilled by vacuum fractionation to obtain a crude product, and refined alpha-hydroxycarboxylic acid ester is obtained by performing neutralization, water washing, and vacuum rectification on the crude product. The alpha-hydroxycarboxylic acid ester prepared by the method has high purity and light color, and can be used as green solvent, surfactant, chiral resolution agent and plasticizer.