The oxidative coupling of methane (OCM) over various alkali metal oxide promoted La2O3/BaCO3 catalysts and the effects of Na2O content on the performance of Na2O-La2O3/BaCO3 catalysts have been studied. It was found that Na2O promoted La2O3/BaCO3 catalysts had the advantages of high CH4 conversion, C-2 selectivity and C2H4/C2H6 ratio. Na2O might affect the properties of the catalysts through electronic and geometric effects. The highest C-2 yield (19.0-20.6%) was obtained with Na2O-9 wt% La2O3/BaCO3 catalysts of 1.0-3.0% Na2O. The effects of reaction conditions on OCM over 3 wt% Na2O-9 wt% La2O3/BaCO3 catalysts have also been investigated. The catalysts were characterized by BET, TPD and XRD. TPD studies on 3 wt% Na2O-9 wt% La2O3/BaCO3 catalysts demonstrated that CO2, CH4 and O-2 could be adsorbed strongly on the catalyst. This might be related to the activation of CH4 and the formation and regeneration of active oxygen species.