Against the backdrop of global carbon emission reduction,ammonia is receiving increasing attention as a cheap,safe,easy-to-store and transport zero-carbon fuel. Utilizing ammonia to replace coal combustion for power generation is an important way to reducecarbon emissions. The combustion characteristics of ammonia with low calorific value,slow combustion rate and high NOx emission arethe difficulties that need to be faced when blending ammonia in coal-fired boilers. In this paper,the experiment of coal-ammonia co-firingunder the condition of deep air classification was carried out in a two-stage drop tube furnace reaction system. The effects of temperature,separated secondary air ratio and ammonia blending method on the combustion characteristics of coal-ammonia co-firing were studied.The experimental results show that when ammonia is added to the primary air,NO emissions increase monotonically with temperature,and sharply increase after 1200 ℃. NO first decreases and then increases with the increase of the separated secondary air,and the optimalseparated secondary air ratio is around 30%. When ammonia is added to the separated secondary air,due to the SNCR effect of NH3,NOemissions are lower below 1100 ℃,which is comparable to pure coal combustion under low co-firing conditions. As the separatedsecondary air ratio increases,NO emissions first decrease and then increase,and the optimal separated secondary air ratio is 20%. xExperimental results have shown that appropriate air distribution can control the NO emissions of coal ammonia co combustion with a cocombustion ratio below 20% without increasing the ratio of pure coal combustion,and the CO emissions and fly ash carbon content arelower than those of pure coal combustion. Therefore,NH3 can be used as an alternative fuel to reduce CO2 emissions from coal-firedpower plants.