TOCs of Longmaxi Formation source rocks and gas-content measurements of shale gas wells in the Zhaotong block, Sichuan Basin showed that the gas content of lower-interval shales is better and the brittleness index of lower-interval reservoirs also indicated adjacent shale formations suitable for stimulation. Based on bulk rock and clay mineral analyses as well as experiments of isothermal adsorption, specific surface areas and aperture distributions, the organic matter (kerogen) in shales was found abundant in well-de veloped nano-pores with an aperture of 2-60nm, which are major contributors to the specific surface area of shales. This can be also implied by the adsorption and desorption curves of kerogens to and from shales because the shape of the curves is generally alike, having a hysteresis loop. However, the clay in shales shows a certain specific surface area whose content has no relationship with the specific surface area of shales. Therefore, with the increase of TOC, the specific surface area of shales increases and their adsorption capacity strengthens as well, resulting in an increase in the saturated adsorption capability and gas content.