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This study aims to elucidate the microscopic mechanism of hydrogen generation from characteristic groups during the low-temperature oxidation of oil-rich coal. FTIR experiments were employed to investigate the changes in characteristic groups with temperature, while quantum chemical simulation was utilized to analyze the reaction characteristics and hydrogen production pathways of hydrogen-rich groups. The results indicate that the characteristic groups associated with H 2 production include aromatic hydrocarbon side chains, carboxyl groups, aldehyde groups, and hydroxyl groups. Two hydrogen production reaction processes, propyl side chain and allyl side chain, were delineated, revealing that the reactivity of allyl side chain is greater than that of propyl side chain. The primary mechanism of H 2 production involves the initial oxygen attack on the methylene structure of both the propyl and allyl side chains in the coal molecule, generating hydroxyl, carboxyl, and aldehyde groups as intermediate products. Subsequently, the hydrogen radical attracts the hydrogen atom on the oxygen atom, leading to O–H bond cleavage, and the combination of two hydrogen radicals forms H 2. [Display omitted] • Key groups driving hydrogen production in coal oxidation are identified. • Pathways for hydrogen generation of propyl and allyl are established. • Hydroxyl radical is a pivotal intermediate in the hydrogen production process. • Hydrogen generation mechanism of low-temperature coal oxidation is achieved. [ABSTRACT FROM AUTHOR]