Abstract: A method of synthesizing glycol diester by reacting a linear aliphatic carboxylic acid and a glycol monoester in the presence of a Lewis acid type catalyst is provided. In the method, after introducing the glycol monoester, the linear aliphatic carboxylic acid and the Lewis acid type catalyst into a reactor, the reaction occurs to produce reaction products and water in the reactor; an excess of the linear aliphatic carboxylic acid forms an azeotrope with water during the reaction to be sent to a condenser through a distillation column; the linear aliphatic carboxylic acid and water passed through the condenser are divided into an organic layer and an aqueous layer in an oil water separator; and the organic layer is returned to the distillation column through a material cycling line and water in the aqueous layer is removed through a water removal line.