The mechanisms of the C(3P)+H 2SHCS+H and C(3P)+H 2S → HSC+H reactions have been studied at the UMP2/631G(d,p),UMP2/6311G(d,p),and G2 levels,and six transition states and three intermediates have been located along the reaction paths. The predicted path for the C(3P)+H 2SHCS+H reaction is:C(3P)+H 2SIM1TS1IM2TS4HCS+H,in line with the reaction process suggested by Lee et al. [1] in which only the intermediates were given. Our energetic results indicate that the C(3P)+H 2SHCS+H reaction is more favorable than the C(3P)+H 2SHSC+H reaction,in agreement with experiment. The mechanisms of the C (3P) + H 2SHCS + H and C (3P) + H 2S → HSC + H reactions have been studied at the UMP2 / 631G (d, p) , and G2 levels, and six transition states and three intermediates have been located along the reaction paths. The predicted path for the C (3P) + H 2SHCS + H reaction is: C (3P) + H 2SIM1TS1 EnerIM2TS4HCS + H, in line with the reaction process suggested by Lee et al. [1] in which only the intermediates were given. Our energetic results indicate that the C (3P) + H 2SHCS + H reaction is more favorable than the C (3P) + H 2S  HSC + H reaction, in agreement with experiment.