Abstract: In order to achieve carbon reduction and reduce the use of coal resources, the co-firing of coal and ammonia has received widespread attention. The competitive characteristics of coal/ammonia co-combustion kinetics under different temperature, oxygen equivalence ratio, and ammonia blending ratio conditions were studied using reactive molecular dynamics (ReaxFF MD) method. The results showed that coal and NH₃ will compete for O₂, and NH₃ has an advantage in the competition, making the reaction 4NH₃ + 3O₂ → 2N₂ + 6H₂O transform to 4NH₃ + 5O₂ → 4NO + 6H₂O, resulting in higher NO emissions. Raising the temperature can reduce the generation of unburned carbon in coal/ammonia co-combustion, promote the homogeneous reduction reaction of NO, and reduce the generation of NO. Reducing the oxygen equivalence ratio can reduce the generation of NO, but it will lead to an increase in unburned carbon generation. Therefore, air staged combustion is important for coal/NH₃ co-combustion. When the NH₃ co-firing ratio is below 40%, NO emissions increase with the increase of NH₃ co-firing ratio. When the NH₃ co-firing ratio is above 40%, NO emissions decrease with the increase of NH₃ co-firing ratio due to the enhanced homogeneous reduction reaction of NO. The competitive effect of coal/ammonia co-combustion kinetics has little effect on the activation energy of coal combustion, but there is a synergistic effect in coal/ammonia co-combustion, which significantly reduces the activation energy of ammonia combustion.