Abstract: CeWTiO_x catalyst is recognized as one of the most promising catalysts for flue gas denitrification. To further clarify the reaction mechanism over it, the NH₃-SCR (selective catalytic reduction) reaction process is studied. At the macroscale, the surface adsorption properties and reaction process of the CeWTiO_x catalyst are investigated through transient and steady-state kinetic experiments, and the reaction activation energy is obtained. At the microscale, density functional theory calculations are employed to further investigate the reaction pathways of NH₃ on the CeWTiO_x catalyst surface. The results demonstrate that NH₃ could be initially adsorbed on the CeWTiO_x surface to form NH₃ species and react with gaseous NO. The presence of gaseous oxygen could significantly promote the SCR reaction. Its reaction rate is nearly 1, 0, and 0.25 order with respect to NO, NH₃, and O₂, respectively. DFT (density functional theory) calculations find that NH₃ has a high adsorption energy on the W-Ce/TiO₂(001) surface. It could be activated by dehydrogenation reaction to generate NH₂^* species. The adsorbed NH₂^* could can initially react with gas-phase NO to form the intermediate NH₂NO, subsequently decomposing into N₂ and H₂O. In addition, NO could directly react with surface O to form NO₂, which has a positive effect on the fast SCR reaction at low temperatures. In summary, the NO conversion reaction on CeWTiO_x catalyst follows the Eley-Rideal mechanism. The modification of W further improves the performance of the catalyst. Therefore, the CeWTiO_x catalyst is a promising material for efficient denitrification.