Selective catalytic reduction of NO X wi th NH 3 (SCR) has been investigated in a fixed-bed reactor with V 2O 5/TiO 2 catalyst. Reaction temperature, contact time, V 2O 5 content in the catalyst and the injection quantity of NH 3 affect the SCR reaction. Increases in react ion temperature and contact time are helpful for SCR reaction, but for their exc essive values the influence of by-reaction will be obvious. The optimum reacti on temperature and contact time are 310?℃ and 200?ms, respectively. NO X re moval increases with n(NH 3)/n(NO X) up to 1.2 and then levels off. When V 2O 5 content in the catalyst is between 1.4% and 4.5% and V 2O 5 is uniformly distributed on TiO 2 carrier, NO X removal increases with the incre ase of V 2O 5 content, but it decreases when V 2O 5 content up to 6.6%. Th e experimental results show that in optimum reaction condition, 90% of NO X can be removed.