Abstract: In the low-NO_x combustion mode, the opposed-fired boiler generates a strong reducing atmosphere in the side water-cooled wall, resulting in a high-temperature corrosion trend on the side water-cooled walls in main combustion zone. To address this issue, methods such as closing-to-wall air and inward deflection of burners near the side wall have been studied and applied, but there are few studies on the effect of pulverized coal concentration near the side wall burner on the reducing atmosphere near the side wall. In order to study the effect of pulverized coal concentration on the high-temperature corrosion rate of the side water-cooled wall of an 1000 MW opposed-fired boiler, the CFD numerical method was used to simulate the furnace combustion characteristics and the reducing atmosphere near the side wall under different coal concentration ratios of the two burners closest to the side wall. The results show that with an increase of the concentration ratio of the second burner to the first burner closest to the side wall leads to an decrease in the CO concentration near the side water-cooled wall in the main combustion zone, and reduce the risk of high-temperature corrosion. Meanwhile, it changes the temperature distribution characteristics of the flue gas and the CO distribution characteristics at the furnace outlet. When the ratio of coal concentration between the two burners closest to the side wall increases from 1∶1 to 3∶1, the average CO concentration decreases from 4.08% to 3.00%, and the maximum value decreases from 8.19% to 6.45%. On the basis of the concentration ratio of 3∶1, with an increase by 12.5% of the secondary air of the first burner closest to the side wall, the average CO concentration in the area near the side wall decreases from 3.00% to 1.89%, and the maximum value decreases from 6.45% to 5.34%. Higher concentration ratio will cause local accumulation of CO at the furnace outlet and increase in local flue gas temperature. The pulverized coal concentration ratio of 3∶1 should be used to balance the improvement of the reducing atmosphere in the main combustion zone and the deterioration of the furnace outlet parameters. At the same time, combustion optimization adjustment is required to avoid the risk of increased CO concentration at the furnace outlet caused by increased pulverized coal concentration of the second burner closest to the side wall. By adjusting the pulverized coal concentration and the excess air coefficient of the side wall burner, the reducing atmosphere of the side water-cooled wall can be significantly improved, which can be used to optimize the control of the high-temperature corrosion rate of the side water-cooled wall in the main combustion zone of the opposed-fired boiler.