Abstract: Incineration is an effective way to achieve the reduction and resource utilization of sludge. Oxy-fuel combustion is considered one of the most promising CO₂ capture technologies. The combination of sludge incineration and oxy-fuel combustion can not only achieve clean and efficient treatment of sludge but also achieve CO₂ capture during combustion. However, only little research has been conducted on oxy-fuel combustion of sludge in fluidized beds reactor. The unique high O₂ concentration and high CO₂ atmosphere of oxy-fuel combustion can have an undeniable impact on the combustion characteristics, pollutant generation and transformation of sludge. In this work, the effects of O₂ concentration, bed temperature, fluidization number, particle size of sludge and moisture content of sludge on the oxy-fuel combustion of sludge and nitrogen oxide （NO, NO₂, N₂O） emissions are systematically investigated on a lab - scale bubbling fluidized bed reactor. The experimental results indicated that under the same O₂ concentration conditions, the diffusion rate of O₂ in O₂/CO₂ atmosphere is lower than that in O₂/N₂ atmosphere, and the combustion rate and burnout characteristics of sludge particles under O₂/CO₂ atmosphere are weaker than those under O₂/N₂ atmosphere. In the same oxygen concentration, the conversion rate of fuel nitrogen in O₂/CO₂ atmosphere is lower than that in O₂/N₂ atmosphere. With the increase of O₂ concentration, the oxy-fuel combustion characteristics of sludge particles are significantly improved, but it also leads to higher NO_x emission and fuel nitrogen conversion rate. High moisture content of sludge can reduce the burnout time and fuel nitrogen conversion rate. An increase in bed temperature and fluidization number can reduce the burning time of sludge particles to varying degrees. High bed temperature and particle size of sludge will enhance the NO_x emissions and fuel nitrogen conversion rate, while high fluidization number will significantly reduce fuel nitrogen conversion.