Abstract: To reduce CO₂ emissions from coal-fired power plants and achieve the goal of "carbon peaking and carbon neutrality", coal and ammonia co-combustion has received widespread attention. In this work, the effect of oxygen containing functional groups in coal on NO emissions during coal/ammonia co-combustion under different temperatures and oxygen equivalence ratios are studied using reactive molecular dynamics simulation. First, the NO emissions of different systems at different temperatures and the mean values of important free radicals OH and NCO are studied. Then, the NO emissions and unburned N emissions of different systems under different oxygen equivalence ratios are studied. Finally, the activation energy of NH₃ combustion in different systems is calculated. The results indicate that O-containing functional groups in coal can promote the oxidation of ammonia to generate NO. The promoting effect of hydroxyl and carboxyl groups is mainly reflected on OH radicals, while the promoting effect of carbonyl groups is mainly reflected on NCO. The generation of NO increases with the increase of temperature. Reducing the oxygen equivalence ratio will significantly reduce the emission of NO and increase the emissions of unburned N. The O-containing functional groups in coal can reduce the activation energy of NH₃ combustion, thereby promoting the oxidation of NH₃ to NO. This study reveals the mechanism of the influence of hydroxyl, carboxyl and carbonyl functional groups in coal on NO generation during coal/ammonia co-combustion in the micro molecular level, providing a theoretical basis for the selection of coal type for coal/ammonia co-combustion in coal-fired boilers.