The invention discloses a method for synthesizing a S-substituted thiobenzoate derivative by Bunte salt. The method takes Bunte salt and benzaldehyde or its derivative as raw materials, under existence of a radical initiator di-tert-butyl peroxide, benzaldehyde, ethyl acetate or acetonitrile are taken as solvents, nitrogen protection is carried out, the materials are fully reacted at the temperature of 100-150 DEG C, after the reaction is completed, a reaction solution is separated and purified to obtain the S-substituted thiobenzoate derivative. The process condition of the method is reasonable, operation is easy and safe, usage of substrates such as thiophenol having bad smell is avoided, three wastes are little, the method is environmentally friendly, a free radical principle is used for synthesizing the product, metal catalysis is not required, and the method is a novel application of a carbon hydrogen activation reaction.