The invention discloses a synthetic method of a benzothiophene[3,2-b]indol derivative. The method comprises the following steps: dissolving N-R3-2-((2-bromophenyl)acetenyl)phenylamine (II) in dimethylsulfoxide, reacting with KSC(S)OEt under the action of CuBr and TBHP to obtain a benzothiophene[3,2-b]indol derivative (I). The formula is shown in the description. The synthetic method has the advantages that the operation is simple, the raw materials are low in price and easy to obtain, the yield is relatively ideal, and the cost is relatively low and the like.