Catalytic activities of K2CO3 supported on several oxides and carbon itself were studied for the combustion of carbon at 673-773 K. K2CO3 supported on a perovskite oxide, La0.8Sr0.2Cr0.5Mn0.45Pt0.05O3 (LSCMP), exhibited higher activity than that supported on the other supports including carbon itself used in this study, the carbon conversion achieving nearly 100% above 723 K. K2CO3 supported on another perovskite oxide, LaMn0.8Cu0.2O3 (LMC), exhibited a high activity comparable to that of LSCMP, although LSCMP and LMC alone showed very limited activity. The mixture of LSCMP with K2CO3/carbon increased the activity and achieved the conversion of 100%. Catalytic active species were found to hardly flow out from the reaction zone when LSCMP was present in the carbon layer. In contrast, they easily flew out downstream as proved by the catalytic combustion of carbon bed placed at downstream when LSC MP was absent in the upstream carbon bed. Roles of LSCMP in the catalytic combustion may be to accelerate reductive activation of alkali metal salts to the active species, to allow sublimation them to the carbon, and to hold the active species in the reaction zone under the catalytic combustion conditions.