Co-firing zero-carbon fuel ammonia is a practical and feasible carbon reduction technology for coal-fired power generation.Taking a 40 MWth pulverized-coal combustion test furnace as the research object, the combustion and NO generation characteristics wereinvestigated numerically under the condition of firing the large proportion of ammonia and without adopting air stagingwhen pure ammoniaand ammonia/ air were injected into the furnace from different locations (flame-root zone, flame-middle zone and flame-tail zone) in thepulverized-coal flame zone. The results show that whether pure ammonia or ammonia/ air mixed gas is injected into the furnace, the carbon content in fly ash increases slightly. Due to the relatively sufficient oxygen content in the main combustion region,the significantNO generation is observed and the NOx concentration at the furnace outlet is higher than that of pure coal combustion. Under the pure ammonia injection method, as the ammonia injection location moves from the flame-root region to the flame-tail region, the carbon content infly ash and the NOx concentration at the furnace outlet gradually decreases. However, under the ammonia/ air mixture injection method, asthe ammonia injection location moves from the flame-root region to the flame-tail region, the carbon content in the fly ash and theNOx concentration at the furnace outlet gradually increases. Considering the burnout and NOx formation characteristics, it is recommendedto feed pure ammonia into the furnace from the tail area of the coal powder flame, and the ammonia/ air mixture is fed into the furnace fromthe flame - root region, which not only can effectively reduce the effect of co - firing ammonia on the burnout characteristics ofpulverized-coa, but also inhibit the NOx generation.