Abstract: The technology of preparing catalysts through molten salt electrolysis with high temperature and strong metallurgical combination has significant advantages under extreme service conditions such as high temperature, high pressure, and strong acids/alkalis. In this study, ruthenium-carbon (Ru/C) composites were prepared by electrolysis of RuCl₃·nH₂O and CO₂ in molten LiCl-KCl-2%CaO mixed salt using a co-electric reduction method. Theoretical analysis indicated that RuCl₃·nH₂O and CO₂ could be effectively electrolyzed in molten salt, and co-electrodeposited self-assembled into Ru/C composite powders. Ruthenium was easier to be electrolyzed than carbon. The results of XRD, SEM, HR-TEM and EDS analysis showed that RuCl₃·nH₂O exhibited an extremely low solubility in LiCl-KCl-2%CaO molten salt and existed in a state similar to an oil-water mixture under gas disturbance. Under this molten salt system, the co-electrodeposition of ruthenium and carbon might still be achieved, and they could self-assemble into Ru/C composite powders. By adjusting parameters such as temperature and electrolytic cell voltage, the composition, content and morphology of Ru/C composite powders could be effectively controlled. This research provides a new preparation route for Ru/C composite catalyst materials with great application prospects.