The NH3-SCR activities of zirconia containing V2O5/WO3-TiO2 catalysts have been studied before and after aging treatment. On fresh catalysts, the addition of zirconia increases high temperature activity and N-2 selectivity but decreases low temperature activity. Interestingly, zirconia prominently enhances the NH3-SCR activities of aged catalysts, with 10 wt%ZrO2 containing catalyst exhibits the highest NO conversions and N2 selectivity in the temperature range of 150-550 degrees C. The catalysts were characterized by XRD. SEM, XPS, DRIFTS and NH3-TPD. SCR kinetic studies were also conducted to understand the mechanistic features of the zirconia modified catalysts. The main results show that the addition of zirconia inhibits the shrinking of catalyst surface area and the growth of TiO2 crystallite size, and therefore improves the thermal stability of V2O5/WO3-TiO2 catalysts. These advantages of zirconia additive can essentially benefit the catalysts performance with high temperature durability. (C) 2011 Elsevier B.V. All rights reserved.