We studied the chemical mechanism for the formation of (NS)-N-2 in the interstellar medium was by using the CCSD/6-311++G(d,p) and CCSD(T)/6-311++G(3df,3pd) levels of theory. To the best of our knowledge, this is the first detailed study of the chemical mechanism for the formation of 2NS. Several reactions proposed in this article are spin-forbidden. They were treated with the Landau-Zener theory and by the MRCI methodology. The following reactions paths proposed in this article are energetically favorable: (1) (NH)-N-1 + (SH)-S-2 -> cis-(HNSH)-H-2 -> TS1 -> trans-(HNSH)-H-2 -> TS2 -> (H2NS)-H-2 -> TS3 -> (NS)-N-2 + H-2 and (2) N-4 + (SH)-S-1 -> (NSH)-N-1 -> TS13 -> (HNS)-H-1 -> (NS)-N-2 + H-2. However, the latter reaction, N-4 + (SH)-S-1 -> (NSH)-N-1, is spin-forbidden, and its probability of occuring (p(sh)) is zero. The chemical mechanism for the formation of (NS)-N-2 in the interstellar medium is now presented in more detail, which is of great importance.