Abstract: As a storage carrier for renewable energy, ammonia can be co-combusted with hydrocarbon fuel for large-scale reduction of CO₂ emission. In this work, the effect of NH₃ on polycyclic aromatic hydrocarbons (PAH) generation during ethylene oxidation is studied using the reactive molecular dynamics simulations. The results reveal that the generation of PAH exhibits a stage characteristic, which includes the formation, growth, and nucleation process of PAH. Ammonia addition does not significantly affect the generation and consumption of PAH precursors (C₁-C₅ hydrocarbons), and therefore has little impact on PAH formation. Ammonia addition enhances the decomposition reactions of nitrogen- containing PAH molecules, which in turn inhibits growth of PAH, but does not significantly affect the distribution of aromatic ring structures in PAH. The introduction of N atoms by ammonia addition leads to a decrease in the number of intermolecular connections between PAH molecules through two-dimensional boundaries. However, However, it promotes an increase in the parallel layer structure generated through three-dimensional stacking, thereby reducing the stability of PAH. In summary, the reason why ammonia doping inhibits the growth of PAH is that the growth rate of PAH slows down and the stability of PAH polymerization decreases.