The static flux chamber method was applied to study natural emissions of methane to the atmosphere in the Luntai fault region of Yakela Condensed Oil/Gas Field in the Tarim Basin,Xinjiang Municipality, northwestern China. Using an online method, which couples together a gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/C/MS), 13C/12C ratios of methane in flux chambers were measured and showed that methane gases are liable to migrate from deep oil/gas reservoirs to the surface through fault regions and that a part of the migrated methane, which remains unoxidized can be emitted into the atmosphere. Methane emission rates were found to be highest in the mornings, lowest in the afternoons and then increase gradually in the evenings. Methane emission rates varied dramatically in different locations in the fault region. The concentrations increased gradually, which reveals that methane released from the fault region might come from thermogenic methane of the deep condensed oil/gas reservoir.