A new type of semidry flue gas desulfurization (FGD) process without waste water treatment was developed with a powder-particle spouted bed reactor. Fine sorbent powder slurries were continuously fed to a bench scale experimental spouted bed in which coarse particles were fluidized. These slurries were fluidized and dried. SO2 sorbent was reacted with SO2 gas and entrained from the bed and collected by bag filters. Slaked lime and slaked dolomite were used as SO2 sorbent. In this study the effects of static bed height, superficial gas velocity, stoichiometric ratio of SO 2 in simulated gas to feeding sorbent, difference between temperature of bed gas and wet bulb temperature of gas, that is, approach to saturation temperature and medium particle size on SO2 removal, are investigated. Among these factors, the stoichiometric ratio Ca/S and the approach to saturation temperature are the most important factors. SO2 removal is significantly improved by reducing the approach to saturation temperature. When the Ca/S ratio is greater than 1.2 and the approach to saturation temperature is less than 13 K, more than 95% SO2 removal is realized. In this experiment, the removal of SO2 increased with static bed height or decreased with superficial gas velocity. This is due to the longer apparent residence time of gas in the dense bed of particles. When coarse particles were normally fluidized in the spouted bed, the effect of the size of medium coarse particles in the bed on SO2 removal was not observed.