The near-wall air (NWA) technology is effective for resolving the high-temperature corrosion on water tube walls in large-scale utility boilers. A numerical investigation was performed to study the effect of NWA on combustion and hightemperature corrosion in an opposed firing pulverized-coal 300 MW e utility boiler. The consistency between the in situ measured and simulated CO distribution tendencies proved that the current simulation methods were reliable and appropriate. NWA not only reduced the peaks of the CO and H 2 S concentrations but also significantly decreased the zone with high CO and H 2 S near the side walls. The NWA injection weakened the reducing atmosphere on the side wall by 40%. NWA presented a slight impact on the gas temperature and the nitrogen oxide (NO x ) concentration at the furnace outlet and led to an obvious increase in unburned carbon. The flow ratio of the NWA was analyzed from 3% to 12%. Considering the unburned carbon, CO, and H 2 S distribution, the appropriate NWA ratio was approximately 6%. High NWA ratio was beneficial to the reduction of the corrosive gases near the side walls. However, this reduction resulted in an increase in unburned carbon. A serious increase in CO and H 2 S concentration was observed in the ash hopper zone near the side wall when the NWA ratio exceeded 9%. This increase was caused by the growth of the recirculation zone in the ash hopper near the side walls, which resulted in high temperature and low O 2 concentration.