The invention relates to the technical field of fly ash decarburization and discloses a fly ash fluidized bed combustion decarburizing device comprising a fly ash material bin, an air blower, an electric heating device, an air powder concentrator, a spiral feeding machine, a hearth, an ash cooler, a cyclone separator, a material return valve, an air heat exchanger, a dust remover, an induced draftfan and a chimney. According to the differences in the aspects of specific gravity and particle size between carbon not burned out and burned-out carbon in the fly ash, the fly ash is carried by hotair to enter an air powder concentrator to be screened, the large-particle and high-carbon-content fly ash falls into the bottom of the air powder concentrator to undergo a next procedure, so that only a part of fly ash needs to be re-combusted, and the work efficiency of reducing the carbon content of the fly ash is improved; and meanwhile, the carbon content in the fly ash combusted in the hearth is increased, the fly ash in the hearth can be stably combusted to emit a large amount of heat, and the utilization ratio of the fly ash is improved.