The invention discloses a synthetic method of a tasimelteon intermediate. The synthetic method comprises the following steps dissolving a compound 1 as shown in a formula 1 which is shown in the description, sodium chlorite and trichloroacetic acid into an organic solvent A, and reacting for 1 to 3 hours under -20 to -10 DEG C, thus obtaining a compound 2 as shown in a formula 2 which is shown inthe description; dissolving the obtained compound 2 as shown in the formula 2 which is shown in the description in an organic solvent B, adding in a chiral catalyst (S)-diphenyl proline, a borane reagent and trimethyl borate, and reacting for 4 to 6 hours at 20 to 40 DEG C under the protection of N2, thus obtaining a compound 3 as shown in a formula 3 which is shown in the description; dissolvingthe obtained compound 3 as shown in the formula 3 which is shown in the description in an organic solvent C, adding in an alkaline matter, and reacting for 2 to 4 hours under the condition of 20 to 40DEG C, thus obtaining a compound 4 as shown in a formula 4 which is shown in the description, wherein the alkaline matter is added in an aqueous solution form. According to the synthetic method disclosed by the invention, the reaction conditions are mild, the operation is simple and convenient, the yield is high, the chemical selectivity is good, the production cost is low, the method is suitablefor industrial production, and higher practical application value and higher social and economic benefit are obtained.