Due to the rapid growth of sludge discharge in recent years and serious pollution to the environment,improving the utilization level and harmless treatment capacity of sludge has become a research hotspot. The coupling combustion of coal and sludge has become an effective measure on reduction,harmless and resource disposal of sludge. A coal power plant coupled with sludge incineration system based on circulating flue gas was proposed,sludge was incinerated in an incinerator instead of being added to the pulverized coal boiler,and the high-temperature circulating flue gas of the pulverized coal boiler was used to promote sludge incineration.The combustion characteristics and heavy metal migration characteristics of sludge in the system were studied by tube furnace,thermogravimetric analyzer and X-ray fluorescence spectrum analyzer.The effects of moisture content on combustion characteristics and the effects of furnace temperature and gas composition on the heavy metal migration characteristics of sludge were analyzed. The results show that the increase of moisture content brings negative effects on sludge combustion and the increase of furnace temperature is conducive to the conversion of strongly volatile heavy metals into gaseous state,thereby reducing the residual rate. The increase of O2 volume fraction brings different effects on the residual rate of different heavy metal. The increase of volume fraction of CO2 will increase the residual rate of heavy metal because high concentration of CO2 would decrease the combustion temperature,and the heavy metal is converted to stable metal oxides and decrease the porosity of residual chars. On the contrary,the increase of H2O volume fraction decreases the residual rate of heavy metal because the presence of H2O improves the combustion temperature and porosity of chars.