A new catalyst for NH3 selective catalytic reduction of NO , which is prepared by impregnation method that Cu and special additives were loaded on the special Ti-Al-O composite carrier . We aslo inspect the effect of the catalyst''s operation condition on its NH3-SCR activity under the condition of simulation of nitric acid tail gas , and discuss the effect of H 2 O on its activity . The result shows that the catalyst has fine middle temperature activity , NO conversion can be 99.5%under the condition of space velocity 10 000 h-1 , temperature 180 ~ 220 ℃ , n( NH3/NO) 0.8 , O2 volume fraction 5.5% , NO volume fraction 200 × 10-6 , and the NO conversion lowers to 14% , after putting in water under 200 ℃ , input water volume fraction is 12.3% , but NO conversion could restore to 99.5% after stopping inputting water for 4 h .