Shale of different sedimentary facies has different geological characteristics, which leads to different gas-adsorption capacity. Based on the isothermal adsorption experimental data, geochemical parameters and pore structure characteristics shale of marine, marine-continental transitional and continental, the gas-adsorption capacity and influencing factors of shale of different sedimentary facies are compared and analyzed. In general, the order of shale gas-adsorption capacity is marine facies > continental facies > marine-continental transitional facies. Organic matter content, kerogen type, thermal evolution degree, pore structure, mineral composition, temperature, pressure and humidity all affect the adsorption capacity. Organic matter and clay minerals are the carriers of adsorbed gas, in which organic matter is the main adsorption carrier, so the higher the content of organic matter, the higher the content of adsorbed gas. The influence of maturity on the adsorption capacity of shale shows a ""two-stage"" mode: when the maturity is below the critical value, the adsorption capacity increases with the increase of maturity, above the critical value, the adsorption capacity decreases with the increase of maturity. The type of organic matter determines the development potential of organic matter pores, and the degree of thermal evolution affects the development degree of organic matter pores by controlling hydrocarbon generation and expulsion. There are obvious differences in the type and maturity of organic matter in shale of the three types of sedimentary facies, which is an important reason for the difference of their adsorption capacity. Temperature and pressure affect the adsorption of shale by changing the adsorption-desorption equilibrium. Water molecules reduce the amount of adsorbable gas by occupying more space.