In order to investigate the influence factors of DeNOx behavior in SCR(selective catalytic reduction) catalysts, with the aid of CFD (computational fluid dynamic) coupled with chemical reaction dynamics, a full-processing simulation and validation tests were conducted on the catalytic substrate. The results show that the temperature is the major factor to influence the conversion efficiency. The optimal temperature for SCR reaction is from 350 to 450℃. Space velocity has a certain influence on conversion efficiency of SCR at low temperature. Increasing NO2 concentration can improve the conversion efficiency, but the volume concentration of NO2/NOx need to be controlled within 50%.