In recent years, multiple exploration breakthroughs have been made in the Maokou Formation of the Sichuan Basin. Currently, the overall exploration level is low. The type and distribution of sedimentary facies are still unclear. The characteristics and formation mechanism of the reservoir are unclear. Techniques such as core observation, pore permeability testing, conventional and cast thin section identification were used to clarify the sedimentary and reservoir characteristics of the 2nd Member of the Maokou Formation in the front of the Longmen Mountains in western Sichuan and to explore the main controlling factors of high-quality reservoirs. Research shows that the 2nd Member 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 shoals 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 are the development areas of high-energy dolomitized platform edge sand debris shoals. The reservoir lithology of the upper sub section of the Maokou Formation is mainly composed 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 storage space consists of intergranular dissolution pores, intergranular dissolution pores, intragranular dissolution pores, and expansion fracture pores. The second section of the Maokou Formation is Ⅱ to Ⅲ porous reservoir. The reservoir foundation is composed of high-energy beach deposits. The leaching and dissolution of atmospheric fresh water during the contemporaneous period is the key to reservoir formation. The reservoir has been improved and maintained through shallow burial dolomitization.