Recently, ammonia has garnered significant attentionaround the world as an effective zero-carbon fuel and hydrogen storage medium. To reduce carbon emissions in coal - fired power plants, the use of zero - carbon fuel blends shows great promise. Investigatesthe combustion behavior of ammonia coal co-firing under the deep-air staging mode. Specifically, the temperature field, component concentration field, and nitrogen oxide emission in the furnace at varying α coefficient conditions are investigated, while maintaining the totalexcess air coefficient at 1.2. The study analyzes four cases with α coefficients equal to 0.696, 0.840, 0.912, and 0.996 respectively. Thetemperature field reveals that as the α coefficient decreases, the ignition position of the first stage of pulverized coal combustion advances.However, the length of the high-temperature flame formed is shortened, and the temperature near the ammonia injection port is notablylower. When α = 0.696, the pulverized coal flame and ammonia combustion flame are distinctly separate, but as α improves, the boundarybetween the two gradually becomes blurred. Decreasing the α coefficient forms a longer reduction zone upstream of ammonia fuel injection,leading to a lower oxygen concentration of ammonia fuel at the moment of injection, hence reducing the probability of ammonia oxidationpath. However, as the α decreases, there is a corresponding decrease in burnout in the furnace,which includes CO emissions concentration, fly ash carbon content, and ammonia escape. However, the influence is very limited in this simulation. Statistical analysis ofNOx concentration in the furnace showed that NOx emissions significantly decreased as α decreased. Furthermore, the highest H2 concentration in the furnace reached 2% under α = 0.696, led to a significant enhancement of ammonia decomposition reaction. Since the consumption reaction of ammonia depends on three global reactions, improved decomposition reaction can reduce the direct participation inoxidation for ammonia. Increased H2 production also enhances the possibility of nitrogen oxide reduction, leading to further decreases inNOx emissions. Ultimately, utilizing the air depth classification method can optimize the temperature and oxygen concentration within theammonia combustion area, contributing to achieve the low NOx emissions in the furnace.