Abstract: A series of Cu(x)/Hβ catalysts were prepared by the impregnation method and the effect on the performance of the catalysts for the selective catalytic reduction of NO with NH₃ (NH₃-SCR) was investigated. Characterization techniques such as XRD, N₂ adsorption-desorption, NH₃-TPD, NO-TPD, H₂-TPR, EDS and XPS were used to investigate the physical and chemical properties of the catalysts and the reason of the decrease of catalyst activity in the presence of SO₂. It was shown that the catalyst Cu(3)/Hβ, the Cu loading was 3% and Cu(2)/Hβ, the Cu loading was 2%, exhibited the better catalytic activity when the initial reaction material contained no SO₂ and SO₂, and t₉₅ was 169 and 225 ℃, respectively. The analysis results of the catalyst before and after the reaction showed that the main reason for the decrease of catalyst activity in the presence of SO₂ was that the ammonium sulfur salt which was formed by the reaction of SO₂ and NH₃ in the low reaction temperature covers the catalyst active center.