A novel SOM process was used to prepare CeNi5 and La x Ce1−x Ni5 hydrogen storage alloys directly from their mixed oxides. The electrolytic reduction was carried out in molten CaCl2 system at 1000°C. The reduction mechanism was investigated by analyzing the chemical compositions and the phase constitutions of the intermediate products of electrolysis. The results suggested that the reduction of NiO–CeO2 may take place in two steps: first, NiO was reduced into Ni and CeO2 reacted with CaCl2 to form CeOCl, then Ni reacted with CeOCl leading to the formation of CeNi5. It was found that the reduction rate increased while decreasing the pressure load of the mixed oxide pellets. Furthermore, CeNi5 could not be produced if the pressure load was lower than 10MPa. It was also found that the pellets of NiO–CeO2 could be completely reduced to CeNi5 alloy by the SOM process, which was greatly excelled than FFC process. The successful preparation of La x Ce1−x Ni5 (x =0–1) alloy reported here suggests that the SOM process may be promising for the industrial application of producing such alloys.