The pore structure of coal reservoirs is the main factor influencing the adsorption–diffusion rates of coalbed methane. Mercury intrusion porosimetry (MIP), low-pressure nitrogen adsorption (LP-NA), low-pressure carbon dioxide adsorption (LP-CA), and isothermal adsorption experiments with different macerals were performed to characterize the comprehensive pore distribution and methane adsorption–diffusion of coal. On the basis of the fractal theory, the pore structures determined through MIP and LP-NA can be combined at a pore diameter of 100 nm to achieve a comprehensive pore structural splicing of MIP, LP-NA, and LP-CA. Macro–mesopores and micro-transitional pores had average fractal dimensions of 2.48 and 2.18, respectively. The Langmuir volume (V_L) and effective diffusion coefficients (D_e) varied from 31.55 to 38.63 cm³/g and from 1.42 to 2.88 × 10⁻⁵ s⁻¹, respectively. The study results showed that for super-micropores, a higher vitrinite content led to a larger specific surface area (SSA) and stronger adsorption capacity but also to a weaker diffusion capacity. The larger the average pore diameter (APD) of micro-transitional pores, the stronger the diffusion capacity. The diffusion capacity may be controlled by the APD of micro-transitional pores.