Abstract: This paper summaried predecessor's study results about determining the origin of natural gas, and the shortcomings with available methods were pointed out. The author deems that carbon isotopic composition of methane and its it isoseries compounds contributes to do it. Only integreted geochemical interpretation with detailed geologic interpretation can we truly understand the origin of it,including its source rock and maturity etc. Otherwise,an incorrect

Key words: Origin of natural gas, lsofope, Geochemical interpretation, Composite petroleum geologic interpretation