Abstract: N₂O have been paid attention to not only one of the greenhouse gas but also destruction ozone at stratosphere. N₂O is released more at the process of combustion at circulating fluidized bed （CFB）. Recent years, as refuse fuel combustor CFBC was used widely. With the refuse fuel combustion more and more, the studies of N₂O formation characteristics had been a new focus. The sludge combustion was observed in the small scale quartz CFB combustion system in Dec. 1995. The experimental result shown that 1) N₂O emission is over 1000ppm at 850℃ in CFB; 2) the conversion rate of fuel-N of sludge converting NO and N₂O is lower than coal; 3) N₂O emission was influenced by O₂ concentration in flue gas.