Abstract: By analysing on the formation,evolution and sedimentary distribution characteristics of the West Sichuan Depression since the Late Triassic and the deformation of the Longmenshan Thrust Belt,it was considered that the Longmenshan Thrust Belt was in the environment of compressive stress field during the Indosinian period,and formed the NEE-oriented and uplift-depression alternated tectonic belt in the Early-Middle Yanshanian period under the action of sinistral compresso-shear stress.The fissures and microfissures formed in the upfolded belts greatly improved the reservoir capacity of dense sandstone,and were favorable to the enrichment and accumulation of oil and gas.