Simultaneous dry removal of SO2 and NOx from flue gas has been investigated using a powder-particle fluidized bed. In a process of flue gas desulfurization by use of solid sorbents such as FeO (dust from a steel plant) and CuO, the smaller the particle size of sorbents, the higher the expected SO2 conversion. In a powder-panicle fluidized bed (PPFB), fine particles less than 40 mu m in diameter fed into the bed are fluidized with coarse particles. But only the fine particles are entrained from the bed, and their residence time in the bed is remarkably long. The reduction of NOx with NH3 in the fluidized bed is catalyzed by coarse particles or both coarse and fine particles. In this study, PPFB was applied to simultaneous dry SO2/NOx removal process, and several kinds of sorbents or catalysts were evaluated in a PPFB. Using the selected sorbents and catalysts, kinetic measurements were made in the temperature range of 300 to 600 degrees C, SO2 removal efficiencies were affected by reaction temperature, sorbent/S ratio, and static bed height. NOx removal efficiencies in excess of 95% were achieved at NH3/NOx mole ratio of 1.0. When FeO was used as sorbent, SO2 conversion increased with increasing temperature and reached 80% at 600 degrees C.