The advantage of CFBC(Circulating fluidized bed combustor) is that it can apply to various fuel sources including the lower rank fuel and remove SOx by means of direct supply of limestone to the combustor without additional desulfation facility. In this paper, we denote characteristics of fly and bed ash to reuse finer limestone usually abandoned(used spec[Coarse LS] 0.1mm under 25%, new spec[Fine LS] 0.1mm under 50%). According to the results, the chemical composition of fly ash was as follows; $SiO_2;40.8%,;Al_2O_3;31.9%,;CaO;10.7%,;K_2O;4.46%$ in the case of coarse limestone and $SiO_2;41.1%,;Al_2O_3;31.3%,;CaO;10.9%,;K_2O;4.66%$ in the case of fine limestone. The chemical composition of bed ash was as follows; $SiO_2;54.2%,;Al_2O_3;33.1%,;CaO;1.56%,;K_2O;4.34%$ in the case of coarse limestone and $SiO_2;53.8%,;Al_2O_3;32.6%,;CaO;2.21%,;K_2O;4.45%$ in the case of fine limestone. It showed that there was no significant change in chemical composition. And it is conformed that there was no significant change in particle size and shapes.