Abstract: This paper takes the double air distributor of circulating fluidized bed boiler as the research object, numerical simulation software is applied to study the cold working condition of boiler, the influence of primary air velocity on furnace pressure, the influence of secondary air speed in the inner lower layer on the gas flow field in the furnace, and the influence of the primary air velocity deviation at both sides on the turn over bed were analyzed.The analysis results can provide reference for this type of circulating fluidized bed boiler operation.