For investigating NO reduction activity of an catalytic filter, the catalytic performance was measured under the presence of SO2 and H2O, respectively or simultaneously in the simulation gas composed of NO, NH3, and air. The catalytic filter was prepared by coating V2O5-WO3/TiO2 catalyst on the pore surface of SiC filter element of which the superior performance for the particulate removal was well known. At the temperature below 260 ℃, the catalytic activities were enormously decreased under the presence of SO2 and H2O, respectively or imultaneously, compared with those under the cases of the absence of SO2 and H2O. However, the presence of SO2 promoted the performance of the catalytic filter above 320 ℃ with showing the NO conversion better than 99.8% for the NO inlet concentration of 500 ppm and at the face velocity of 2 cm/s. In particular, the presence of water showed high NO conversion higher than 99% up to high temperature of 380 ℃. This effect of water was explained by the reason that it retarded the ammonia oxidation which is the main step into the formation of N2O. The initial NO reduction activity of the catalytic filter maintained for the duration of 100 hours in the presence of SO2 and H2O. Therefore, it was concluded that the catalytic filter was promisingly useful for the industrial NOx reduction catalyst in order to treat the particulate and NO simultaneously.