Abstract: In order to clarify the microscopic dynamics mechanism of hydrogen sulfide (H₂S) adsorption and diffusion in coal, and to reveal the influence mechanism of different temperatures and pressures on the molecular adsorption and diffusion characteristics of coal adsorbed H₂S, based on the Giant Canonical Monte Carlo (GCMC), Molecular Dynamics (MD), and Density Functional Theory (DFT) methods, the adsorption-diffusion characteristics of H₂S in the gas-fertilized coal macromolecule model at temperatures ranging from 273.15 K to 313.15 K and pressures ranging from 1 to 1 000 kPa were investigated using Material Studio software. The results showed that the saturated adsorption of H₂S decreased from 38.34 mL/g to 31.85 mL/g at an increase in temperature from 273.15 K to 313.15 K, which is a 16.93% decrease. The effect of temperature on adsorption is most sensitive when the pressure is 1 kPa. The most significant interaction energy increased from −39.391 kJ/mol to −34.301 kJ/mol when the pressure was increased from 1 kPa to 1 000 kPa at a temperature of 293.15 K. With the pressure increased, the most significant interaction energy increased first rapidly and then slowly. During the adsorption of H₂S, the isocratic heat of adsorption of H₂S was in the range of 36.63−41.43 kJ/mol, which is a physical adsorption. The isocratic heat of adsorption showed a negative exponential change with increasing adsorption volume. The Gibbs free energy ΔG of H₂S was from −3.57 to −24.57 kJ/mol, and the entropy of adsorption ΔS was from −0.126 to −0.194 8 kJ/(mol·K). The absolute values of ΔG and ΔS linearly decreased with increasing adsorption amount, and the adsorption spontaneity of H₂S and the chaos of the system decreased. The interaction energy of H₂S with gas-fertilized coal was ranged from −492.47 to −3 390.95 kJ/mol, which was dominated by van der Waals’ energy accounting for 58.67% of the total energy, and supplemented by electrostatic energy accounting for 41.33%. As the adsorption capacity increased, the absolute value of interaction energy increased, and the changes in adsorption capacity and interaction energy were consistent. H₂S interacted most strongly with the carboxyl group, followed by the hydroxyl group. Double layer adsorption of H₂S occurred around —OH, —COOH, —C=O. The temperature was increased from 273.15 K to 313.15 K. The diffusion coefficient of H₂S molecules was increased from 1.066×10⁻¹⁰ m²/s to 2.025×10⁻¹⁰ m²/s, and the activation energy of diffusion was 11.206 kJ/mol. An increase in temperature can lead to the opening of previously closed pores and channels, increasing the connectivity of cracks. As the temperature rises, it increases the average free path of H₂S molecules, enhancing their diffusion ability. The limiting heat of adsorption of H₂S was 42.898 kJ/mol. The H₂S concentration distribution showed a multi-peak structure, and H₂S was distributed in a laminar structure in the gas-fertilized coal macromolecule model. H₂S had hydrogen bonding with —OH, —COOH, and —C=O reactive groups on the coal body, and there was a weak chemisorption of H₂S in the early stage of adsorption.