A series of W-Zr-O-x/TiO2 catalysts were prepared by a precipitation method and tested for selective catalytic reduction (SCR) of NO by NH3. These samples were characterized by XRD, NH3-TPD, H-2-TPR, SEM, Py-IR, XPS and in situ DRIFTS, respectively. Results showed that the catalyst with the ratio of WO3 and ZrO2 15:1 could exhibit excellent catalytic performance. The maximum catalytic activity of 15W1ZT was 100% at 400-550 degrees C and at a border temperature range 330-600 degrees C the catalytic activity was higher than 90%. The catalytic activity still remained even under the condition of H2O and SO2. The high catalytic performance of 15W1ZT catalyst could be attributed to a series of superior properties, such as more acid sites, more hydrogen consumption, and the higher proportion of chemisorbed oxygen and oxygen vacancies. Furthermore, in situ DRIFTS in different feed gases show that the SCR reaction over 15W1 ZT followed L-H mechanisms and monodentate nitrite, bi-dentate nitrate and the amide species (-NH2) were the main reaction intermediates.