The carbonate reaction of some alkaline-earth chlorides was investigated by a carbonate agent injection method in LiCl-KCl eutectic salts containing both SrCl 2 and BaCl 2 and LiCl molten salts containing SrCl 2 . The effects of the injected molar ratio of a carbonate agent (Li 2 CO 3 or K 2 CO 3 ) and the temperature (450-750°C) on the conversion efficiencies of the strontium and barium chloride to their carbonates were determined. The forms of strontium and barium carbonate resulting from the carbonate reaction with carbonate agents were identified by XRD and SEM-EDS analyses. In these experiments, the carbonate agent injection method can carbonate strontium and barium chlorides effectively at over 99% under LiCl-KCl eutectic and LiCl molten salt conditions. For LiCl-KCl eutectic molten salts, carbonation efficiency was more favorable in the case of K 2 CO 3 injection than in the case of Li 2 CO injection, where strontium and barium were carbonated in the form of Ba 0.5 Sr 0.5 CO 3 . For LiCl molten salts, strontium was carbonated in the form of SrCO 3 by Li 2 CO 3 injection.