The carbonation and decarbonation of the Ca solid reactant prepared by the natural limestone powder were analyzed about the effect of annealing temperature on the reactivity and the durability in repetitive operation. The solid reactants annealed at 1073 K and lower had the larger reproducible pore volume in the range from 10 to 25 nm, and showed the higher conversion of carbonation. The solid reactants annealed at 1273 K indicated the excellent durability of repetitive cyclic procedure, which was comparable to that of the reactant prepared by the metal alkoxide method.