A series of key stationary points of potential energy surface (PES) for the CH₃S+NO system was calculated at the G3(MP2) level. The calculations reveal three intermediates, seven transition states and nine product channels. With the stationary point energies and TST-RRKM theory, the reaction rates were calculated in the temperature range of 200～1700 K, and the gas phase reaction mechanism of CH₃S+NO was discussed. At low temperature, the production of CH₃SNO is the main reaction channel. At high temperature, H-abstraction mechanism to give products of CH₂S+HNO is the dominant reaction channel, and the other products might be neglected. This result is compared with the experimental value.

Key words: ab initio, methylthiyl, TST-RRKM, reaction mechanism