Abstract: The generation of natural gas has the character of owning various geological origins.In this paper,the defining process of dissipated soluble organic matter is summarized,the occurrence conditions and generation approaches are analyzed and the effective abundance lower limit is pointed out.It is believed that the dissipated soluble organic matter is the main gas source during the stage of high evolution degree and has broad exploration prospect.It was pointed out that the light hydrocarbon in cracked gas generated from dissipated soluble organic matter has much naphthenic hydrocarbon but it from accumulated soluble organic matter has no naphthenic hydrocarbon and has more paraffin hydrocarbon than benzene and naphthalene series.It was also attested that not only silicate rocks but also carbonate rocks have catalysis for the soluble organic matter generating gas,so the dissipated soluble organic matter is more potential than accumulated soluble organic matter to generate gas.Based on geology reality,the assessment method for dissipated soluble organic matter is indicated to make it operable to evaluate the potential of generating gas.