The title reaction has been investigated in detail by using B3LYP method with 6-311+G* basis sets. Three paths yielding the same product cyc-ScS 2 + ( 1A 1) are initiated from two cis-trans isomers of collision complex S–Sc +···S–CO and another interesting channel proceeds via a linear transition state initiated from the head-to-head collision of the two S atoms and leads to a linear adduct Sc +–S 2 ( 1∑ +) that can dissociate into products Sc +( 3D) and S 2( 3∑ −). The features of observed product cross-sections and their changes among reaction energy range are well explained by the calculation results with consideration of that the calculated barrier of the lowest energy pathway was overestimated by 18.0 kJ/mol.