The roles of WO3 and SiO2 in Ce-V catalysts supported on TiO2 comprised tungsten-silica were investigated systematically for NH3-SCR (selective catalytic reduction) and NH3-oxidation at high temperatures. When SiO2 and WO3 were added to TiO2, the surface area of Ce-V/TWS was maximized and the formation of Ti-O-Si bond reduced nanoparticle size compared to without SiO2. The Ce-V/TWS surface had greater abundance of catalytic defects and surface oxygen species via XPS results. Increasing the (V4+ + V3+) fraction increased the catalytic activity, which is attributed to the enhanced SCR performance at a wide temperature range due to the addition of WO3 and SiO2 to TiO2. The catalysts using the TWS supports exhibit high catalytic activity, since WO3 and SiO2 can promote redox properties. It was shown that Ce-V/TWS was the most suitable catalyst for selectively producing N-2 via thermodynamically unavoidable NH3 direct oxidation as the temperature increased. In addition, hydrothermal aging effects were investigated for the Ce-V/TWS catalyst prepared by TiO2 supports including WO3 and SiO2 (comparison with vanadium-tungsten/titania). This study demonstrates the feasibility of utilizing WO3 and SiO2 in the TiO2 support as a possible way to increase catalytic activity and N-2 selectivity in NH3-SCR at high temperatures.