The effects of alkali salt (NaCl. KCl) on the calcination and sulfation reaction of CaCO3 and limestone have been determined using a thermogarvimetric analyzer (TGA). The pure CaCO3 of agent grade decomposed at 640 ℃, however decomposition temperature of CaCO3 impregnated with NaCl exponentially decreased with the increased NaCl loading. Calcination rate of alkali salt loaded CaCO3 increased loading up to 5 wt% but it decreased slightly when the loading increased above 5 wt%. The sulfur capture capacity increased with temperature up to 700 ℃ but it decreased with temperatures above 700 ℃. The sulfation rate of alkali salt loaded CaCO3 increased with alkali salt loading for both NaCl and KCl. The sulfur capture capacity of calcined lime impregnated with NaCl increased with increased temperature up to 650 ℃ for 10 wt%-NaCl loading, and for 2, 5 wt% NaCl loading the capacity increased up to 700 ℃. The alkali salt activity followed the reaction order m of grain model and the activity of calcination was ranked as: NaCl>KCl> no additive, and that of sulfation was ranked as : NaCl (5 > 10 > 2 wt%) > KCl(5 > 2 wt%)> limestone impregnated with NaCl > limestone.