Abstract: This invention relates to a method for preparing tetrahydrothiophen, consisting in that tetrahydrofuran is reacted with a sulphidation agent, elementary sulphur or phosphorus sulphides, with the stoichiometric ratio of the above-named substances, and at a temperature of 175.degree.-215.degree.C, with subsequent isolation of the end product. The interaction between tetrahydrofuran and elementary sulphur can be realized in the presence of a red phosphorus additive which increases the yield of the end product. In the described method a non-toxic and safe (with respect to explosion) sulphidation reagents is used which markedly improves the labour conditions. The method is simple, requires no complicated process equipment, and can be effected under milder conditions as compared with the known methods.