The selective catalytic reduction (SCR) of nitric oxide with excess ammonia in the presence of oxygen on silica-supported vanadium oxide catalyst was studied in a packed-bed reactor, and a mathematical model was proposed for the processes occurring in the reactor. Experimental data were presented for evaluation of the accuracy of the proposed model. Good agreement was observed between the measured and calculated values of the conversion in the outlet of the reactor. Once the validity of the proposed model was verified, it was used to examine the effects of different parameters such as feed temperature, inlet feed composition, and gas hourly space velocity (GHSV) on the conversion of NO over V2O5/SiO2 catalyst for practical application. The results for the employed catalyst showed that high NO conversion occurred at temperatures of 280-300C, GHSV less than 2000h-1 (STP), and O2 concentration greater than 10% v/v. These results clearly demonstrate the high potential for this catalyst to be applied commercially for the control of NOx emissions from flue gases of different sources.