The invention relates to a synthesis method of a psychotropic drug-amitriptyline intermediate compound, i.e., a compound 2-(2-phenylethyl)benzoic acid shown in a formula (III), and the formula (III) is described in the description. The synthesis method concretely comprises the following steps: enabling a compound shown in a formula (I) to react with a compound shown in a formula (II) in a bicomponent organic solvent at the temperature of 70-100 DEG C in presence of a catalyst, a nitrogen polydentate ligand, an oxidant and organic alkali, and carrying out aftertreatment after the reaction is finished so as to obtain the compound shown in the formula (III), wherein the formula (I) and the formula (II) are described in the description, X is halogen, Y is alkali-metal element, and R is H or analkyl group having 1-6 carbon atoms. After the method is adopted, a high yield and high purity target product can be obtained by means of a specific comprehensive reaction system, so that a novel route is provided for the synthesis of the amitriptyline intermediate; the synthesis method has good research value and industrialization amplification potential.