Semidry desulfurization process with in situ supported sorbent preparation was studied. The effects of bed inventory, slurry sprayer height above the distributor, and slurry spray method on desulfurization efficiency were tested. The results showed that desulfurization efficiency for 28kg of bed inventory could reach 98.84% for Ca/S molar ratio of 2.5. This result was approximately seven times higher than the result without bed material because ultrafine Ca(OH)(2) particles in the lime slurry adhered to the bed material surface and formed the supported sorbent. A lower slurry sprayer height and countercurrent slurry spray could reach an even higher destilfulrization efficiency. The desulfurization efficiency of this proposed process was approximately 30-40% higher than that of the supported sorbent prepared by the original hydration and drying method at high Ca/S molar ratio due to better contact efficiency between water and sorbent particles.