In order to explore the catalytic oxidation activity of Cu-Ce/TiO₂ catalyst before and after CO pretreatment, the CO conversion rate of the catalyst under different sintering flue gas conditions is tested based on a fixed bed reactor, and the property changes and catalytic reaction mechanism of the catalyst after CO pretreatment are explored by XRD, XPS and in-situ FTIR characterization. The results show that the catalytic activity of the catalyst pretreated by CO is significantly higher than that before pretreatment, and the conversion rate of CO reaches 99% at 180 ℃. The number of Cu⁺, Ce³⁺ and oxygen vacancies on the surface of the catalyst after CO pretreatment is higher than that before pretreatment, which determines that the catalyst after CO pretreatment has better catalytic activity. The reaction mechanism of CO oxidation catalyzed by Cu-Ce/TiO₂-CO catalyst is MvK mechanism. In addition, NO, SO₂ and H₂O can affect the catalytic oxidation performance of Cu-Ce/TiO₂-CO, among which SO₂ has the greatest effect, and all these effects are reversible.