Abstract: In response to the national "dual carbon" policy, so as to reduce carbon dioxide emissions from coal-fired power plants, the co-combustion of coal and ammonia has received widespread attention. Based on molecular dynamic simulation, researches were conducted on the changes in the types and quantities of coal-ammonia pre-pyrolysis products at different temperatures, and the migration pathways of nitrogen element during pre-pyrolysis and combustion processes, so as to obtain the influence mechanism of pre-pyrolysis temperature on NO_x emissions. Results show that, the increase of pre-pyrolysis temperature leads to the decrease of NO_x emissions during combustion. Due to the increased temperature can enhance the interactions between coal and ammonia during pre-pyrolysis, the production of CN and HCN increases with the increase of pre-pyrolysis temperature, and the conversion of hydrogen atoms in coal into H₂ is promoted by the interactions between coal and ammonia. Meanwhile, the increase of pre-pyrolysis temperature can promote the pyrolysis of NH₃ to produce N₂, reducing the nitrogen sources available for NO_x formation. The reduction in NH₃ content decreases the generation of HNO, thereby lowering NO_x emissions. Additionally, the increase of pre-pyrolysis temperature can promote the production of H₂. The presence of H₂, on the one hand, can consume a large amount of O₂, reducing the formation of NO_x during combustion, on the other hand, can accelerate the conversion of HNO to N₂, thus reducing the generation of NO from HNO decomposition.