Abstract: Based on the conventional analysis of organic geochemistry, and debris gas, components of natural gas, fingerprints of light hydrocarbon, and carbon isotopesetc.,the gas source of the Jurassic natural gas in the west Sichuan Depression, the Sichuan Basin is studied and correlated in this paper. It is suggested that the gas in the depression was mainly derivd from the T₃x₄-T₃x₅ assemblages.