The development of a highly efficient and cost-effective strategy for the fixation of organic sulfur, as well as radioactive metal nuclides holds great significance in the treatment of organic contaminants. Herein, ternary molten carbonate (Li2CO3-Na2CO3-K2CO3) was used for treating simulated waste resins containing Fe3+ and Co2+ (Fe-Co-CERs). The FT-IR and XPS analysis showed that the significant conversion process of organic sulfur in molten Li2CO3-Na2CO3-K2CO3 was sulfonic acid group (−SO3-) → sulfuryl group (−SO2-) → sulfur bond (−S-). The TG-DTG curves and the activation energy (E) revealed Fe3+ and Co2+ possess self-catalysis during the oxidation of Fe-Co-CERs, wherein distinctly facilitated the decomposition of −SO3- and −S- structures. The produced SO2 was further absorbed by molten carbonate to generate sulfate, which was confirmed by the observed increase in SO42- and the corresponding decrease of CO32–. The conversion of LiNaSO4 to K3Na(SO4)2 revealed that Li2CO3 is to function as a sulfur catcher at temperatures below 400 °C, which then as a crucial heat transfer medium at temperatures above 400 °C. The predominant forms of Fe and Co at 700 °C were primarily Co8FeS8, FeS, and CoS, which underwent oxidation to form CoFe2O4 and CoSO4 at 800 °C. The retention rate of S, Fe and Co reached 94.36 %, 97.48 % and 98.35 %, respectively. This molten salt oxidation (MSO) strategy exhibits promising potential for the treatment of organic contaminants containing sulfur and multiple metal elements.