Abstract: In order to improve utilization efficiency of the bottom slag waste heat of circulating fluidized bed boiler units, a two-stage bottom slag waste heat utilization system coupled with a fluidized bed slag cooler and a drum slag cooler is proposed, and a mathematical model for calculating the efficiency and power generation of the system is established. Taking a 350 MW supercritical circulating fluidized bed boiler unit as the research object, the performance calculation and analysis have been carried out. The results show that the waste heat utilization efficiency of the system is relatively high, with a minimum of 62% and a maximum of over 96%. The increasing of power generation can be up to above 3. 6 MW. The system can also alleviate the problem of insufficient condensate flow in some units, and will play an important role in the construction of large-scale circulating fluidized bed boilers in the future.