The objectives of this study were to investigate the characteristics of limestone calcination and sulfation in a fluidized bed reactor with bed temperature and air velocity. The experimental results were presented as follows ; First, the bed temperature had a great influence on the calcination and the sulphur retention of limestone and paper sludge. In paper sludge, tile optimum conditions in calcination and desulfurization temperature was at 800℃ and in natural limestone, that was at 850℃ or 900℃. Second, as air velocity increased, the specific surface area of particles decreased. But the difference of ,surface area according to air velocity was not too large. The specific surface area of paper sludge was larger than that of natural limestone. Third, as air velocity increased, the absorbed amount of sulfur dioxide decreased. And the absorbed amount of ,sulfur dioxide by paper sludge was larger than that of by natural limestone. Therfore, we knew that paper sludge was excellent absorbent and bed temperature had a great important variable on the calcination and sulphur retention in a fluidized bed.