As one of the common gaseous pollutants, CO has seriously affected human healthy life and green economic development. Extensive research has shown that the supported metal oxide catalysts can perform efficient catalytic oxidation of CO. However, how to obtain catalysts with high CO oxidation performance from numerous oxides and to reveal the key factors impacting CO oxidation activity from microscopic aspects have been the topical concerns of researchers. In this paper, we investigated the CO oxidation reactions on the surface of a series of supported transition metal oxide M_xO_yH_z/TiO_2 catalysts using density functional theory (DFT) calculations, and analyzed the key factors influencing the CO oxidation reactions conducted on the catalyst surface. Then the CO oxidation activity of partially supported oxides was calculated and predicted. The results showed that the adsorption energy (Eads) of CO molecules on the catalyst surface and the oxygen vacancy formation energy (E_ov) of the active sitejointly determine the CO oxidation activity of the catalyst. The CuO/TiO_2 catalyst exhibited the highest CO catalytic oxidation activity; VO_3H, CrOH_3, ZrO_2, and WO_3/TiO_2 displayed the lowest activity; the remaining catalysts were intermediate in activity. Then activity testing experiments were carried out and the results were found to be consistent with the DFT calculations.