Cast Fe-Mo-S wear-resistant alloy with and without CeO 2 was prepared with a medium frequency inducting oven. The effect of CeO 2 on the friction and wear properties of the alloy was examined with a block-on-ring friction and wear tester. The action of CeO 2 in the formation of surface film and its effect on the characteristics of the surface film were investigated by means of X-ray diffraction (XRD), electron probe microanalysis (EPMA), and X-ray photoelectron spectroscopy (XPS). It was found that the wear resistance of the cast Fe-Mo-S alloy was increased by doping with CeO 2 , while the frictional coefficient at higher load was decreased. These results can be attributed to the enhanced production of sulfide and oxide surface film and the retarded oxidation of MoS 2 in the surface film. Such an enhancement and retarding action arose from the action of the CeO 2 . However, the microhardness of the cast Fe-Mo-S alloy was slightly affected by CeO 2 .