Abstract: Investigating the difference in adsorption properties of shale gas and coalbed methane plays a guiding role in exploration and development. In this paper, isothermal adsorption experiments respectively for coal and shale rock samples with various grades of maturity and contents of TOC were conducted, and the results show that total organic carbon (TOC) is the major factor influencing the gas adsorption capacity of shale, compared to shale with equivalent maturity, coal has much higher adsorption capacity, largely due to the differences in reservoir-forming characteristics, substance composition and pore structures. The abnormal adsorption of shale may be supported by other adsorption theories.