The synthesis process of S-(3)-hydroxy tetrahydrofuran includes the following steps: mixing methanol and thionyl chloride, adding solid L-malic acid and heating to room temperature for dissolving L-malic acid; heating reflux, adding alkali to regulate pH to 7-8, extracting, drying, filtering and decompression concentrating to obtain dimethyl malate; reacting dimethyl malate in LiCl/borohydride/lower alcohol reducing system to produce butantriol; filtering to eliminate solid and adding acid to obtain solid inorganic matter precipitate; and cyclizing butantriol at high temperature and under the catalysis of p-toluene sulfonic acid to produce S-(3)-hydroxy tetrahydrofuran. The present invention has new reducing system for producing butantriol, and is simple and suitable for industrial production.