Calcium was loaded on Illinois No. 6 coal by different methods; hydrothermal treatment, hydration treatment, and physical mixing, and then its effectiveness as a desulfurizing agent was compared under various experimental conditions. The amount of SO2 emitted from the coal hydrothermally treated with lime was quite small during the oxidation in comparison with the physical mixture of coal with Lime. In the case of coal with hydrated lime, the amount of SO2 emission was as small as that of hydrothermally treated coal when compared at the same level of calcium loading. Calcium loaded by hydrothermal. or hydration treatment can act as a good sulfur sorbent, Chemical species produced by these treatments were identified by using X-ray diffractometer and a scanning electron microscope attached with energy-dispersive X-ray analyzer, and we attempted to clarify the effectiveness of each species for SO2 sorption.