Several shale samples were selected from the Silurian Longmaxi formation from the Yibin region in the Sichuan Province of China. Shale samples were examined by geochemical analysis, rock mineral composition analysis and desorption experiments. Isothermal adsorption experiments were carried out by the gravity method and the carbon isotope fractionation of methane was investigated by measuring the value of δ ¹³C₁. The characteristics of carbon isotope fractionation of methane at different temperatures were compared. Moreover, the desorbed gas was collected at the same exploration sites and the gas composition and values of δ ¹³C₁ were measured. Carbon isotope fractionation of methane is influenced by shale reservoir characteristics, especially the higher the total organic carbon (TOC), the greater value of δ ¹³C₁. Mineral components and migration diffusion may influence the adsorption capacity of carbon isotope fractionation of methane. In low temperature environments, the degree of carbon isotope fractionation is higher. The range of the carbon isotope fractionation of methane in-site is obvious and has a positive correlation between the content of CH₄. Moreover, the gas composition changes regularly with the increase of desorption time.