The corrosion resistance of stainless steels in a molten carbonate bath was investigated by the immersion and semi-immersion test at 650℃ for different exposure times. The corroded samples were analyzed by using the x-ray diffractometer to identify the phases present. Characterization of the corroded scale was carried out with scanning electron microscopy and electron probe microanalysis. Weight loss was decreased as the contents of chromium and nickel increased in stainless steels. Corrosion resistance of austenitic stainless steels was superior to those of ferritic stainless steels and duplex stainless steels, because nickel formed a solid solution in lithium iron oxide which suppressed the outward diffusion of iron through inner Cr2O3 layer.