The reduction properties and oxygen storage capacity (OSC) of Ce-Fe mixed oxide (Ce/Fe = 4/1) were investigated. When TPR/OSC cycle was repeated, Ce-Fe mixed oxide gave a new reduction peak at 600 degrees C, suggesting the enhancement of the reducibility of iron ions. This was accounted by the formation of a solid solution and the participation of Fe2O3 as catalyst for the reduction of Ce-Fe mixed oxide.