With the rising of IGCC and the second generation PFBC-CC, and with the development of tech-nology of staged combustion to lower emission of NOx, the desulfurization efficiency under reducingatmosphere is raised. In this paper, with the application of the fly-ash recycle and tworstage combus-tion technologies in a fluidized bed combustor, the desulfurization test under reducing atmosphere isdescribed. Meanwllile, ammonia injection test was also conducted. Results show that desulfurizationunder reducing atmosphere has higher efficiency, and ammonia injection denitrification effect is veryperfect. With the rising of IGCC and the second generation PFBC-CC, and with the development of tech-nology of staged combustion to lower emission of NOx, the desulfurization efficiency under reducing atmosphere is raised. In this paper, with the application of the fly-ash recycle and tworstage combus-tion technologies in a fluidized bed combustor, the desulfurization test under reducing atmosphere isdescribed. Meanwllile, ammonia injection test was also conducted. Results show that desulfurization under reducing atmosphere has higher efficiency, and ammonia injection denitrification effect is veryperfect.