Thermodynamic equilibrium limit in the system of methane oxidative coupling was studied. The Van′t Hoff equation was used to study the influence of temperature. PR equation was used for calculating the fugacity of each compound. With thermodynamic model and related data, aimmimg at the minimum of Gibbs free energy in this system, the thermodynamic property of the methane oxidative coupling were calculated at ideal condition. The methane conversion, selectivity and yields of other compounds at equilibrium were studied. The influences to different compounds in the system caused by different temperatures， pressures， methane and oxygen molar ratio have been tested. It is found that in this system H2 and CO are easy to get while C2 products (C2H6 and C2H4) are difficult. Not only CO and H2 but CO2 and H2O have the same changing trend. The higher temperature, lower pressure and lower methane and oxygen molar ratio can help to improve the methane conversion. And it is advantageous for C2 products at the condition of higher temperature, pressure, methane and oxygen molar ratio.