The inlet duct and insulation design of AQC boiler in cement kiln waste heat power plant have a significant impact on boiler operation and heat utilization. To reduce heat loss and improve waste heat recovery efficiency, insulation measures need to be taken for the inlet duct. This article analyzes the heat transfer mechanism of the AQC boiler inlet duct, establishes a physical field model of the AQC boiler inlet duct, and conducts numerical simulation calculations using software of Fluent. The temperature field of the AQC boiler inlet duct with different inner insulation layer thickness and the linear relationship curve of the hot air temperature with the length of the duct are obtained. The numerical simulation results indicate that the most economical and reasonable design scheme for insulation layer thickness is when the thickness of the inner insulation layer of the inlet duct（?3 620mm×8mm）of the AQC boiler is 70mm, and the thickness of the wear-resistant casting material and outer insulation layer is 100mm.