This investigation was carried out for the determination of rate controlling mechanism of SO₂ sorption from a synthetic gas by prototype alkalized alumina. The theoretical approach was also conducted from the unreacted core shrinking model, while the measurement of rate of SO₂ sorption was gravimetically employed by a torsion balance. The experimental results pointed that, the unreacted core shrinking model could be applied to SO₂ removal from flue gas by alkalized alumina and its rate was controlled initially by chemical reaction by both chemical reaction and diffusion, in the intermediate stage, and by diffusion at the end.