The use of SrF2 as a dopant of Y2O3 catalyst for oxidative coupling of methane apparently increased C-2 selectivity and yield under the same conditions. However, it simultaneously decreased both the acidity and basicity of the catalyst, indicating that there was no direct relationship between catalytic performance and acidity/basicity of the catalyst. The interaction between SrF2 and Y2O3 phase took place more or less in the course of the catalyst preparations, as proved by XRD results of the fresh and used catalysts. The intrinsic anionic vacancies in the catalyst would be favorable to the activation of molecular oxygen under the reaction conditions. ESR and in situ Raman spectral results showed that superoxide ion (O-2(-)) adspecies was observed on the surface of Oa-pretreated 67 mol% SrF2/Y2O3 catalyst at 973 K, which may be the active oxygen species for oxidative coupling of methane.