In recent years, multiple exploration breakthroughs have been made in the Maokou Formation of the Sichuan Basin, demonstrating good resource potential.Studying the sedimentary characteristics and reservoir formation mechanism of the 2nd member of the Maokou Formation in the front of the Longmen Mountains in western Sichuan has guiding significance for future oil and gas exploration.Based on field profiles, drilling, logging, and seismic data, this study analyzed the sedimentary and reservoir characteristics of the Qixia Formation in the front of the Longmen Mountains in western Sichuan using methods such as core observation, conventional and cast thin section identification, and pore permeability testing, and explored the mechanism of reservoir formation.Research shows that the 2nd section of the Maokou Formation in the front of Longmen Mountain in western Sichuan develops in a northwest southeast direction.The southern and middle sections of Longmen Mountain are the development areas of high-energy sand debris shoals on the gentle slope edge of the lower sub section of the second section of Maokou Formation.The middle and northern sections of the Longmen Mountain in the upper sub section of the second section of the Maokou Formation develop high-energy dolomitized platform edge sand debris shoals.The reservoir lithology of the upper sub section of the Maokou Formation consists of residual bioclastic sandstone dolomite, bioclastic grain dolomite, and residual grain dolomite.The reservoir lithology of the lower sub section of the second section of the Maokou Formation is mainly composed of residual sandstone dolomite and residual grain dolomite.The types of storage spaces include intergranular dissolution pores, intergranular dissolution pores, intragranular dissolution pores and expansion fracture pores.The second section of the Maokou Formation is a type II and III porous reservoir with medium to thin layers and low porosity and permeability.The high-energy beach sedimentation forms the basis for reservoir development.The leaching and dissolution of atmospheric fresh water during the quasi contemporaneous period is the key to reservoir formation.The dolomitization during shallow burial period improved and maintained the reservoir.