Abstract: Located in the west of Sichuan basin,the western Sichuan depression is a suite of sedimentary sequences developed in the Karnian of late Triassic,representing the evolutions of the passive continental margin(the basin under the Xujiahe Formation),intraconti-nental foredeep basin(the basin above the Xujiahe Formation)and intracontinental depression(J~K).Therefore,its formation and development are related to the closure of the Tethyan oceanic basin.The authors modelled on the varying patterns of the depression during its geological history,hence to clarify the formation,migration,accumulation and dispersion of the natural gas in the western Sichuan Depression.