Li-doped sulfated-zirconia catalysts were found to be effective for oxidative coupling of methane (OCM). The catalyst performances depend on the sulfate content and calcination temperature. A maximum C-2 yield is attained over the catalysts, which contain 6 wt.% sulfate and calcined at 923-973 K, being closely related to the preparation conditions of sulfated-ZrO2 as solid super-acids. When the performances of the Li-doped sulfated-ZrO2 (Li/SZ) catalysts were tested at 1023 K as a function of reaction time, both the C-2 and COx selectivities remained constant over the range of 8 h, but the CH4 conversion decreased from 17.5% to 11.9%. The nature of Li/SZ catalysts for the OCM was investigated by X-ray diffraction, XPS, and NH3 and CO2 TPD measurements. It could be postulated that the sulfated-ZrO2 surface could play an important role in the formation of a catalytically active structure by Li-doping.