Abstract: It is of great significance to investigate the non-catalytic reduction of nitrogen oxides （NO_x） regarding its emission control.The non-catalytic reduction behavior of nitrogen oxides was investigated in a high-temperature fixed-bed reactor under the conditions of reaction temperature （800–1400℃），gas conditions V_CO∶V_H2=3∶1–1∶3),the volume ration reducing gas concentration (V_NO∶V_CO+H2=1∶1–1∶6,and residence time （2.7–7.2 s）,and kinetic simulations were carried out by using Chemkin software.It is shown that the reduction rate of NO increases with increasing temperature in the temperature range from800 to 1 400℃，especially from 1 300 to 1 400℃.Increasing the usage of reducing gas is favorable to increase the reduction rate of NO,and prolonging the residence time of the reducing gas can also enhance the reduction rate of NO;by comparing the NO reduction reactions of CO and H₂ respectively,it can be seen that the reduction ability of H₂ is stronger than that of CO.Increasing the concentration of H₂ in the gas mixture helps to increase the NO reduction rate.Comparison of the reduction effects of CO and H₂respective gas and the mixed gas of CO and H₂ by kinetic calculations reveals that there is a synergistic effect on NO reduction between CO and H₂,and the mixed gas can enhance the NO reduction rate by about 6%.The reaction pathways for NO reduction by CO and H₂ are determined by kinetic analysis of the elementary reactions of the NO reduction process.It is demonstrated that the reason for the greater reduction capacity of H₂ than CO is due to the high rates of all the elementary reactions in which it is involved.After further pathway analysis,the key reaction step in the synergistic reduction of NO by CO and H₂ lies in the generation of HONO as intermediate product.