Abstract: Shale gas shows have been observed from the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in several wells in Xichang Basin. The drilling results indicate that gas content of Wufeng Formation-first member of Longmaxi Formation (Long 1 member) is relatively good, showing promising potential for shale gas exploration and development. By comprehensively applying core observation and thin section data, and integrating with logging interpretation, the high-quality shale is classified and the stratigraphic sequence,sedimentary facies and depositional pattern are studied, so as to primarily evaluate shale gas potential of Long 1 member in Xichang Basin.The study results show that: (1) The high-quality shale of Wufeng-Longmaxi Formation is composed of five thin layers ① - ⑤ ; (2) The highquality shale is divided into two third order sequences. Deposits of bioclastic beach microfacies of tidal flat facies and siliceous mud shelf microfacies of deep-water shelf facies were developed in SQ1, while SQ2 was composed of lime mud shelf and limy sandy mud shelf deposits of deep-water shelf facies; (3) The development of high-quality shale was controlled by the deep-water shelf environment during the deposition period of Wufeng-first sub member of the first member of Longmaxi Formation (Long 1₁ sub member), which had high organic carbon content,high silica content and rich graptolite; (4) The shale gas accumulation in high-quality shale of Wufeng-Longmaxi Formation is affected by three key factors, i.e., development degree of fault zone, burial depth of high-quality shale and distance between the high-quality shale to fault zone.