Abstract: K₂O and K₂SO₄ are loaded on the catalyst V₂O₅(1%)/AC (V1/AC) by the method of wet immersing followed by drying. The effect of potassium compounds on the catalytic performance of V1/AC for the low temperature SCR of NO by NH₃ was investigated. It was found that both K₂O and K₂SO₄ as ultrafine particles loaded in V1/AC can cause the catalyst deactivation. The adsorption of NH₃ on the catalyst, especially the portion of weakly adsorbed NH₃, is inhibited remarkably by the loading of potassium compounds. The inhibition by K₂SO₄ is moderate, as compared with that by K₂O; this is also in accordance with the extent of their effects on the catalytic activity. K₂O brings on little change in the surface oxidizability of V1/AC, the catalyst deactivation by K₂O is a result of the inhibition of NH₃ adsorption. Comparatively, the loading of K₂SO₄ may enhance the possibility for the adsorbed NH₃ being oxidized to NO by O₂.