2, 3-Dimercaptosuccinic acid-S₂³⁵ has been synthesized as follows:Sodium sulphidc-S³⁵(Ⅰ) was oxidized with iodine to give sulphur-S³⁵(Ⅱ).The latter was converted into phosphorous pentasulphide-S₅³⁵(Ⅲ) by the action of red phosphorous.Interaction of Ⅲ and acetic acid gave thiolacetic acid-S³⁵(Ⅳ).2, 3-Bis-acetylthiosuccinic acid-S₂³⁵(Ⅴ) was obtained by the addition of compound IV to acetylenedicarboxylic acid.Upun hydrolysis of V the desired 2, 3-dimercaptosuccinic acid-SZS(Ⅵ) was obtained.This method has been found to be satisfactory for the synthesis with the advantages of convenience and safety in handling.