Abstract: The MgO/ZrO₂ catalysts were prepared by impregnation method. The effect of catalysts calcination temperature on the catalytic oxidation of NO was investigated by the characterize of XRD, SEM and N₂ adsorption/desorption and catalyst activity test. The effects of O₂ content and catalyst particle size on the conversion of NO were further investigated. The catalysts before and after the reaction under the optimal experimental conditions were analyzed in combination with FTIR characterization. The results indicated that the MgO/ZrO₂ catalyst only shows the characteristic peak of ZrO₂ at different calcination temperatures; When the calcination temperature was ≤ 300 ℃, MgO/ZrO₂ catalyst was amorphous. Nevertheless, with the increase of calcination temperature, zirconia in the catalyst gradually transforms from amorphous to tetragonal zirconia. The results of catalyst activity test showed that the catalyst calcined at 800 ℃ was more favorable for the catalytic oxidation of NO. The catalytic efficiency of MgO/ZrO₂ for NO oxidation was not related to the specific surface area, but related to the slit formed by catalyst accumulation. When the O₂ content was 5%, the catalyst particle size was 20 mesh, the conversion rate of NO increased with the increase of reaction temperature; The best NO conversion of 96% was achieved when the reaction temperature was 300 ℃.