Abstract: In order to improve the operation stability and economy of the 660 MW circulating fluidized bed boiler in a certain power plant, the combustion optimization adjustment test of the boiler was carried out. The results show that the current boiler operating oxygen is low, increasing the total air volume can significantly improve the boiler efficiency, but the increase of air volume is easy to lead to NO_x concentration exceeding the limit value. When the boiler is running at full load, the primary air volume does not need to be adjusted temporarily, and the primary air volume is controlled from 700 kNm³/h to 750 kNm³/h. At 495 MW load, the primary air volume of the boiler should be properly reduced, and it is appropriate to control it below 600 kNm³/h, which can significantly improve the boiler efficiency and reduce NO_x emission. Bed pressure has little effect on improving boiler efficiency, but has a significant negative correlation with NO_x emission. Considering the excessive bed pressure will aggravate furnace wear and increase fan power consumption, the boiler bed pressure should be maintained at 12.5–13.5 kPa during operation. When the amount of loose air and return air decreased from 2400 Nm³/h to 1600 Nm³/h, the efficiency of the separator increased, and the change of boiler efficiency was less than 0.03%. In order to reduce the power consumption of boiler bed and fan, it is recommended to adjust the loose air volume and return air volume to 1600 Nm³/h.