Abstract: Gaseous fuel reburning denitrificationtechnology can effectively reduce the initial nitrogen oxide emission of the boiler. In this paper,aiming at NO_x reduction mechanism of gaseous fuel reburning and its application status in Engineering,the effects of five factors on the reburning effect were analyzed. The typical demonstration projects and their operation effects of gaseous fuel reburning technology in boiler retrofit were summarized. The research at home and abroad shows that the essence of denitrification by gaseous fuel reburning is that hydrocarbons decompose by heat to produce related groups,which collide with NO_x to generate corresponding nitrogen-containing intermediates. At the last,the nitrogen-containing intermediates react with reducing groups to convert part of NO_x into N_2. Specifically,CH_3 intermediate is mainly generated in the process of methane reburning,and the reduction reaction between CH_3 and NO is the key to denitrification,while HCCO intermediate is generated in the process of multi carbon hydrocarbon fuel reburning,and the reduction reaction with NO is the core of reburning. The results show that there are proper ranges of reburning zone residence time,excess air coefficient and temperature during reburning. What′s more,the reburning fuel composition and the mixing characteristics of reburning fuel and NO_x also have a significant effect on the reburning effect. Increasing the residence time of reburning fuel in reburning zone is not only conducive to NO_x reduction,but also conducive to the burnout of reburning fuel. However,the too long residence time in reburning zone will not increase the NO_x reduction rate,but will reduce the combustion efficiency of fuel. The best residence time of reburning zone is 0.6-1.1 s,and the further increase of residence time will not increase denitrification efficiency.The excess air coefficient in the reburning zone has a significant effect on the reburning reduction efficiency and burnout characteristics. The best excess air coefficient in reburning zone is 0.85-0.90.The high temperature of reburning zone is conducive to improving the denitrification efficiency of reburning fuel,and the optimal denitrification temperature in reburning zone is 1 000-1 100 ℃.The composition of reburning fuel is different,and the reduction effect of NO_x is different.The reburning denitrification of hydrocarbon is closely related to its thermal decomposition. Under the same reburning condition,the reburning denitrification performance is completely related to its heating classification rate. The research shows that the presence of multi carbon hydrocarbon can significantly enhance the reduction effect of reburning gas mixture,and the presence of tar and coal char can have obvious catalysis effect on the NO reduction. In addition,the denitrification process of gas fuel reburning is not only affected by the difficulty of chemical reaction,but also related to the diffusion process of reburning fuel in the high NO_x concentration area. Strengthening the mixing characteristics of reburning fuel and NO_x in the reburning area is also conducive to improving the denitrification efficiency.The United States,European Union,Japan and other countries started earlier and achieved remarkable results in the research and engineering demonstration projects of power plant boiler reburning and denitrification. The demonstration projects of natural gas reburning technology transformation of Sichuan Jiangyou Power Plant also proved the feasibility and economy of reburning and denitrification.