The possibility of preparing formed active coke using fly ash from a fluidized bed coal gasifier for flue gas desulfurization was investigated. The study shows that fly ash can be utilized as the feedstock with the addition of some raw coal. The obtained formed active coke exhibits an almost equivalent desulfurization capacity to that from raw coal. In addition, the effects of the pore properties and surface chemical properties of different formed cokes on SO2 removal were analyzed and discussed. The effect factors on the mechanical strength of formed coke and optimal preparation conditions were also discussed.