The primary gas layer of the Maokou Formation of the JLS structure in the Sichuan Basin is a typical pore-fracture carbonate gas reservoir. Natural fractures (mainly tectonic fractures) serve as the critical factor in improving the reservoir's physical properties. The characteristics, formation mechanisms of natural fractures, and their impact on the reservoir are analyzed using the core, thin slice, full microresistivity imager imaging logging, production testing, and the Monte Carlo method multiple approximations. The results show that the fractures in the Maokou Formation reservoir generally refer to shear fractures of a tectonic origin, with the characteristics of a medium scale (10−20 cm), a large inclination angle (45− 90), a high density (greater than 5 m −1 ), a medium opening (1−3 mm), and a low filling degree. There are three primary formation stages of natural fractures in the area, the Indosinian stage (232−210 Ma), the early-middle Yanshanian stage (145−90 Ma), and the late Yanshanian−Himalayan stage (90−0 Ma). The corresponding principal stress directions are NW, near-SN, and NNW, respectively. Natural fractures have a positive effect on the improvement of reservoir physical properties. The fracture's physical parameters show a good positive correlation with the physical properties of the reservoirs. The fracture parameters influence the reservoir's physical properties ranked from biggest to smallest: opening, length, and density. The greater the development degree of fractures, the greater the corresponding natural gas production capacity. The research results provide a new technical method for quantifying the influence of fracture parameters on reservoir's physical properties.