The invention discloses a method for synthesizing (S)-2-benzyloxy-1-propanal. The method comprises the following steps: firstly, enabling (S)-2-benzyloxy-1-propanal to react with ethylenediamine, andobtaining (S)-2-(1-benzoxy ethyl)-4,5-dihydrogen-1H-imidazole; dissolving the (S)-2-(1-benzoxy ethyl)-4,5-dihydrogen-1H-imidazol in anhydrous ethanol, then adding metal sodium under the protection ofnitrogen, and stirring and reacting; and after the reaction is ended, removing the ethanol, slowing adding residues into a saturated oxalic acid solution, uniformly stirring, then refluxing reacting,after the reaction is ended, extract, drying and filtering, removing the solvent, and obtaining a product (S)-2-benzyloxy-1-propanal. The (S)-2-benzyloxy-1-propanal is prepared in two steps; in the preparation process, diisobutylaluminium hydride which is expensive in price and easy to ignite in the after-treatment is not used, so that the operation safety is improved, and the production cost is decreased; and the preparation process is mild and easy in operation, the anhydrous condition for the reaction of a traditional process is not, and the industrialized production is easy to realize.