We systematic investigated the CO oxidation reaction over a single Co atom supported by MoS2 monolayer (Co/MoS2) on the basis of density functional theory calculations and ab initio molecular dynamics simulations. The binding energy of a single Co atom onto MoS2 monolayer is up to 2.80 eV, making the diffusion and aggregation of supported Co atom difficult. For CO oxidation reaction, both Eley-Rideal and Langmuir-Hinshelwood mechanisms are considered. The energy barriers of CO oxidation through the Langmuir-Hinshelwood mechanism for the rate-limiting step of formation the peroxide-like O-C-O-O intermediate is only 0.57 eV. The relatively high CO oxidation activity of Co/MoS2 may be attributed to the strong electronic resonance among the 3d orbital of the Co atoms and the antibonding 2 pi* orbitals of adsorbed CO and O-2. We proposal that the MoS2 monolayer can serve as a defect-free two dimensional single atom catalysts substrate for CO oxidation reaction. It provides not only a large surface ratio, but also a uniform distribution anchoring points for fixing metal atoms as activation sites. We hope that this work contributes to design more effective nonprecious-metal single-atom catalysts for CO oxidation and widen the applications of monolayer MoS2 materials. (C) 2017 Elsevier B.V. All rights reserved.