In order to assess correctly the flux of CH4 emitted naturally from oil/gas basin, a static flux chamber method was applied to study natural emissions of methane to the atmosphere in oil-water interface of Yakela condensed oil/gas field in Tarim Basin, Xinjiang. Using an online method which couples a gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/C/MS) together, 13C/12C ratios of the methane in flux chambers were measured. The results demonstrate that oxidation environments of soil and water are different in the oil-water interface because chambers lie in different places. Even all methane is absorbed by soil in some areas, which leads to the sink of atmospheric methane.