Abstract: The mechanism of NO reduction with CO catalyzed by char was studied via density function theory (DFT). The optimized configurations and stationary points of homogeneous and heterogeneous reactions on the char surfaces of Zigzag and Armchair were obtained. Finally, kinetic analysis for both homogeneous and heterogeneous reactions were carried out. The results show that the activation energy of homogeneous NO reduction reaction is 254.06 kJ/mol, while only 86.94 and 52.16 kJ/mol for heterogeneous reaction on Zigzag and Armchair models, respectively. This indicates that char is able to play an activating role in the NO reduction reaction. The NO reduction reaction on the char surface undergoes four stages of N₂ formation, N₂ release, and two stages of CO₂ release, and finally generates one N₂ molecule and two CO₂ molecules. Moreover, the surface structure of char has a great influence on the characteristics of NO reduction reaction. Compared to Zigzag char surface, NO reduction reaction with Armchair-type has a lower energy barriers and higher reaction rate constants. That is, the NO reacts easily with CO on the Armchair surface.