In this study, sorbent for flue gas desulfurization is prepared using metallurgical dusts (MD) abundant in iron oxides as the main active component, lime as promoter, and amylum as special additive. The reactivity of the sorbent is conducted in a quartz fixed-bed reactor within the medium temperature range of 300 degrees C-750 degrees C under heating and isothermal conditions, while the physical and chemical properties of the sorbent are measured using ICP-AAS, SEM, XRD, and so on. The experimental results indicate that with temperature increasing from 300 degrees C to 750 degrees C, breakthrough sulfur capacity of the sorbent increases from 0.0257 gS/gSorbent at 300 degrees C to 0.1391 gS/gSorbent at 650 degrees C, then decreases to 0.0836 gS/gSorbent at 750 degrees C, and that the removal efficiency of SO2 and breakthrough sulfur capacity of the sorbent depend on the chemical kinetics of Fe2O3 and CaO in the temperature range of lower than 600 degrees C, but on the thermodynamic equilibrium of sulfuration of Fe2O3, the thermal stability of the Fe-2(SO4)(3) and content of CaO in the range of higher than 650 degrees C. Physical and chemical analyses of the fresh and reacted sorents further verify that the effective and dominating component of the sorbent is Fe2O3 within the temperature range of lower than 650 degrees C, while is CaO in higher than 650 degrees C.