The invention discloses a synthetic method of 1,1'-dicaprolactam disulfide. Caprolactam is used as an initiator, and sulfur monochloride and caprolactam inorganic salt are used as raw materials. Sulfur monochloride firstly reacts with caprolactam to form 1,1'-dicaprolactam disulfide and acid; caprolactam inorganic salt is continuously converted to caprolactam under the action of the acid formed bythe reaction; and caprolactam continuously reacts with sulfur monochloride to form 1,1'-dicaprolactam disulfide. According to the method, there is no need to add other types of acid-binding agents, and the raw material caprolactam can be synthesized by itself in the reaction process. The production technology is simple, has strong operationality and simple post-treatment, and has industrial application value. The product is white solid powder in the appearance, and the yield is 88% and above, the purity is 99% and above. The product meets the use requirements.