Abstract: In order to reveal the effect of CO on the reduction of NO by NH₃, experimental and simulation studies were carried out on the NO reduction process by NH₃ at different CO concentrations. Results show that the addition of CO has no significant effect on the NO reduction efficiency below 1 400 ℃ under anaerobic conditions, and above 1 400 ℃, the NO reduction efficiency of the NO reduction process by NH₃ is improved when CO is present in the atmosphere. Under low O₂ conditions, the temperature window of NO reduction by NH₃ process is expanded under low oxygen concentration conditions when CO is present in the atmosphere. Thus, it can still maintain a higher NO reduction efficiency at a high temperature above 1 400 ℃. Under the condition of higher O₂ concentration, when CO is present in the atmosphere, the optimal NO reduction temperature moves to the low temperature, and the NO reduction temperature window narrows. The simulation results show that, under anaerobic and hypoxic conditions, above 1 400 ℃, CO promotes the reaction of NH₂ and CO to generate HNCO, and then HNCO further reacts with OH to generate NCO, and then reduces NO, thereby enhancing the NO reduction process. When the O₂ concentration is high, the generation of OH and O is promoted by CO at a lower temperature, thus ensuring the progress of NH₂ generation and NO reduction process. The temperature increase will accelerate the process of CO and OH reaction to generate H, then promote the reaction of H and O₂, so that a large number of O radicals are generated in the reaction process, and these O radicals are easily oxidized with NH₂. As a result, NO generation is promoted, resulting in a rapid decrease of NO reduction efficiency.