Understanding the role of metal-support interaction for the supported single-atom catalysts is very important in heterogeneous catalysis. Here, Three different CO oxidation mechanisms on Pt/gamma-Al2O3 catalyst were probed by periodic density functional theory (DFT) calculations in detail, namely the reactive O*-O-C*=O intermediate mechanism, the reactive CO3 intermediate mechanism and the Pt-Al3+ double sites mechanism. According to the calculated results analysis, we concluded that the dominant reaction pathway at the low temperatures is the reactive O*-O-C*=O intermediate mechanism. Our results are in very good agreement with the experimental evidence for O*-O-C*=O coverage on Pt/gamma-Al2O3 at room temperature by an in situ diffuse reflectance infrared detector. (C) 2016 Elsevier B.V. All rights reserved.