Hydrogen formed in oxidative coupling of methane(OCM) over BaCO3 and MgO catalysts was measured since the data of H2 selectivity were missing almost in all articles published heretofore.It was found that H2 selectivity achieved about 18%.when C2 hydrocarbon’s selectivity was maintained at 48%-45%over BaCO3 catalyst at the feed molar ratio of CH4/O2=4 in temperature range of 780℃-820℃.Under similar conditions,H2 selectivity was about 14%-16%over MgO catalyst.with C2 selectivity maintained at 41%-42%.Possible routes for hydrogen formation in OCM reaction were discussed.Effect of addition of alkali metallic ions was also investigated.