Abstract: Zigzag carbonaceous model was applied to investigate the heterogeneous reduction mechanism of NO by moderate gasification char through the density functional theory in quantum chemistry method combined with thermodynamics and kinetics. The reaction path of heterogeneous reduction of NO by moderate gasification char were analyzed, and the energy change during heterogeneous reduction, thermodynamic and kinetic analysis were conducted. Research results show that the moderate gasification char is prone to adsorb NO. The process of CO desorption, which provides active sites for NO reduction, is a reaction rate determining step, and need to overcome the maximum barrier(398.03 kJ/mol). The reduction reaction is spontaneous and exothermic reaction in the coal combustion system and takes place in one direction. According to the theory of reaction rate determining step, the progress of the reaction need to overcome the larger activation energy(389.83 kJ/mol), and according to Arrhenius expression, the overall reaction rate is greatly affected by temperature. The higher the temperature is, the faster the reaction rate is, and the more favorable for NO reduction.