Abstract: Aiming at the problems of high carbon content in ash and poor operation stability of 410 t/h circulating fluidized bed( CFB)boilers in A power plant,the main operation parameters such as primary air volume,return air volume and coal particle size were optimized and adjusted,and the optimum combination of boiler operation parameters was explored.. The test results show that the size of the coal entering the furnace is slightly fine and the median diameter is only about 1 037.97 μm. The median diameter of the boiler bottom slag is only375.64 μm,which indicates that the ash-forming characteristics of the coal entering the furnace are better. The running picture shows that the differential pressure value of ash concentration in the upper part of the furnace is as high as about 2.5 k Pa. The excessive fine ash particles in the furnace make the circulating ash volume fluctuate greatly under the influence of primary air volume. In order to ensure the stable operation of the return material of the boiler,the primary air flow through the air distribution plate controlled by the operator is only102 300 m3/h,which is much lower than the design value of 183 000 m3/h,and is also seriously lower than that of the same type of units.The results show that the main reason for the high carbon content of ash slag is that the low primary fluidized air volume makes the combustion in dense phase zone seriously anoxic. In addition,the low primary air flow makes the resistance of the distributor only 2.1 k Pa.Compared with the resistance of the air distributor of the same type of boiler,the resistance of the air distributor is smaller,which results in poor local fluidization and uneven temperature distribution of the boiler. It is suggested that the combustion efficiency of the boiler can be effectively improved by adjusting the size of coal into the furnace reasonably,controlling the median diameter between 2 000-3 000 μm,optimizing the ash concentration distribution in the furnace and increasing the primary air flow.