Based on density functional theory calculations, the catalytic reduction of N2O by CO molecule over the surface of Si-embedded MoS2 (Si-MoS2) is investigated. The calculated adsorption energies reveal that N2O and CO are chemisorbed on the Si-MoS2 due to their strong orbital interaction with the Si atom. Our results indicate that the adsorbed N2O can be easily decomposed to N2 and O* moieties without activation energy. The catalytic activity of Si-MoS2 for removing of O* by CO is studied and it is found that the corresponding energy barrier (0.32 eV) is lower than those on noble metal-based catalysts.