The invention relates to the field of rubber and particularly provides a preparation method of TBSI. The preparation method of TBSI is characterized by taking 2-mercaptobenzothiazole, tert-butylamineand oxygen as reaction raw materials, and reacting in the presence of a nano-copper catalyst to obtain TBSI. Through the method, oxygen is used as an oxidization agent, so that the generation of wastegas and waste liquid is avoided; the nano-copper catalyst is used, so that the reaction efficiency is improved; the preparation method of TBSI is simple and convenient to operate and is capable of preparing TBSI through a one-step method; the manpower and the material resources are saved; the yield of TBSI is greatly increased; the production cost is greatly reduced; meanwhile, no waste gas and no waste liquid are generated; the clean production is achieved; the sustainable development of the industry is achieved; the large-scale industrial production can be achieved.