The xerogel samples were prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) by the sol-gel method. In this investigation, a new molar ratio of H2O/TEOS was determined to be 11.7. Also, the necessary amounts of tri-hydrated copper nitrate and penta-hydrated copper sulfate were added to the solution in such a manner that the concentration of the copper oxide in final solution reach to 10-12 wt %. After ambient drying, the xerogel samples were heated at 400, 600, and 800˚C at a slow heating rate (50°C/h). The structural properties were characterized by Transmission Electron Microscopy (TEM), Brunauer, Emmett and Teller theory for specific surface area determination (BET) and Thermal Program Reduction (TPR) methods at different temperatures. Finally, characterization of nano-composites was studied for NH3 selective catalytic reduction (NH3-SCR) of NO in gas phase. The results were presented the systematic reactivity study of NO reduction by NH3 on dispersed copper oxide nano-composites over silica supports, in order to determine the ability of these materials to convert into harmless species at different temperatures.