Abstract: Due to the high temperature of the discharged slag of circulating fluidized bed unit, the heat loss of the unit is large. If this waste heat can be utilized properly, the thermal economy of the unit will improved greatly. The traditional way to utilize the waste heat of the slag cooler is to recover the heat from the slag to the condensate system. From the point of view of energy consumption, this method is not the most economical.In this paper, a new waste heat utilization method of slag cooler was proposed for circulating fluidized bed heating units, during the heating period, the heat of discharged slag is directly used for heating the backwater of heat supply network, and in non heating period, the heat of discharged slag is still reclaimed to the condensate system The specific implementation of the new scheme was given, which maximized the use of original system and equipment, only added one cooling water pipe in the new scheme, the new system was simple, and the investment was small. The economic analysis of the two schemes was carried out by using the equivalent thermal drop method, and the calculation results show that the new scheme is more economical.