In this study, we investigate desulfurization characteristics of granules made of limestone powder. Their characteristics have been compared with those of crushed limestone which is conventionally used as a desulfurization agent. The granules have larger surface area than crushed limestone, and therefore, are expected to be highly efficient desulfurization agents. The results obtained from the experiments using thermogravimetry (TG) and a fluidized bed demonstrate that the granules are easily calcined (CaCO3 --> CaO + CO2), and have a higher desulfurization rate than the crushed limestone. Furthermore, we calculated the reaction rate costant and activation energy in the initial stage of desulfurization reactions, and the results also show that the granules have a higher activity than crushed limestone. A fluidized bed conducted under similar conditions shows that flying dust formation of the granules is higher than that of the crushed limestone. It is suggested that the granules are powdered in the initial stage of fluidization.