Co-combustion of sludge and coal in circulating fluidized bed (CFB) boilers can not only realize its reduction disposal,but also be used as alternative fuel to reduce the use of coal and realize resource utilization. The effects of operating parameters such as different blending ratio,primary air ratio,and excess air ratio on the combustion efficiency and gaseous pollutant emission of municipal sewage sludge and Xuzhou bituminous coal were investigated on a 0.3 MWth circulating fluidized bed pilot plant. The existing forms and transformation characteristics of nitrogen and sulfur in coal and sludge were discussed,and the components and melting characteristics of fly ash in the process of co-combustion of coal and sludge were analyzed. The XPS results indicate that N mainly exists in the form of pyrrole nitrogen (90.58%) and quaternary nitrogen (9.42%) in sludge. In the bituminous coal,N mainly exists in the form of pyrrole nitrogen. The S in sludge is mainly organic sulfide，while S in bituminous coal mainly is the stable inorganic sulfate. The NO emission decreases while the SO2 emission increases when the proportion of sludge increases during the co-combustion process. The NO emission decreases but barely influence SO2 emission with increasing the secondary air ratio. The NO and SO2 emissions increase while the CO emission decreases when the excess air ratio increases from 1.2 to 1.4. When the proportion of sewage sludge increases from 0 to 100%,the unburned carbon in fly ash increases from 8.09% to 28.26%,while the combustion efficiency decreases from 99.23% to 87.76%. Co-combustion sludge with coal can also decrease the melting temperature of fly ash.