Ab initio MP2 calculations have been carried out to study the activation of methane on lanthanide oxide La2O3. O- and O-2(2-) : are assumed to be the active species on the oxide surface. The possible roles of O-2(-) and O-2(4-) on the oxide surface in C-H bond activation are also investigated. It is shown that the CH4 oxidative dehydrogenation occurs much more readily on O- and O-2(2-) than on O2- and O-2(4-). The results indicate that O- and O-2(2-) : are the active species and therefore support the O- and O-2(2-) : mechanisms assumed for the reactions. The promoter compound containing Br- is found to be favorable for the methane activation.