CeO2/BaF2 was used as the catalyst for the oxidative coupling of methane (OCM). At 800-degrees-C and CH4:O2 = 2.7:1, CH4 conversion of 34% with C2 hydrocarbon selectivity of 54.3% was obtained. XRD measurement showed that partial anion (O2-, F-) and/or cation (Ce4+, Ba2+) exchange between CeO2 and BaF2 lattices occurred. ESR study showed that O- species existed on degassed catalyst. XPS study revealed that, when BaF2 was added to CeO2, the binding energy of Be 3d5/2 was 2.2 eV lower than that in CeO2, and the "electron-enriched lattice oxygen" species was detected. XPS, ESR and Raman study showed that, under O2 adsorbing conditions, O2(2-) and O2- species were detected on CeO2/BaF2.