To improve the water tolerance and activity of traditional Hopcalite catalyst, a series of CuMnOx catalysts with a typical Hopcalite composition, but with part of the Mn element replaced by Sn were prepared and evaluated for low temperature CO oxidation. It is revealed that with suitable Sn replacement, both the moisture tolerance and activity of the catalysts have been evidently enhanced. The best performance is achieved with 8.5 wt% Sn addition. With the incorporation of Sn, the morphologies of the catalysts were changed accompanying the formation of a larger amount of intra-particle mesopores, thus resulting in catalysts with much higher surface area. In addition, more active oxygen species has been formed in the catalysts, as evidenced by H-2-TPR, O-2-TPD and XPS results. Furthermore, the catalyst surface has more exposed Cu2+ cations, thus having stronger ability to adsorb CO molecules. Most importantly, ETIR and H2O-TPD results have testified that the addition of SnO2 can significantly suppress the adsorption of H2O molecules on the surface of the catalysts, hence improving their water resistance at low temperature dramatically. In conclusion, these are believed to be the major reasons accounting for the remarkably improved moisture tolerance as well as activity for Hopcalite catalysts by SnO2 addition. (C) 2016 Elsevier B.V. All rights reserved.