Abstract: Hydrogen-assisted deconstruction enables the directional conversion of complex petroleum hydrocarbon molecules into single-structure chemical feedstocks; however, it is constrained by competing reaction pathways and side reactions. To achieve efficient and precise cleavage of structurally complex hydrocarbons, This review systematically analyzes the mechanistic features and thermodynamic behaviors of key reactions within the reaction network. The results indicate that dealkylation and olefin hydrogenation constitute the primary pathways, while side-chain cracking and aromatic hydrogenation act as parallel competing routes. With increasing temperature, the selectivity of dealkylation increases, whereas side-chain cracking products exhibit a higher equilibrium fraction under identical conditions. Hydrogenation serves as a consecutive step for side-chain scission, in which olefin hydrogenation shows a higher equilibrium conversion, while aromatic hydrogenation is thermodynamically limited and proceeds to a lesser extent. Secondary cracking of longer-chain alkanes and ring-opening of naphthenes are identified as consecutive side reactions; the former exhibits a higher equilibrium conversion, while the latter is constrained by the thermodynamic feasibility of isomerization. Future work should focus on thermodynamic constraints of the reaction network to elucidate pathway competition and enable directed regulation of reaction pathways. Keywords: hydrogen-assisted deconstruction; complex hydrocarbons; reaction mechanism; thermodynamic properties ; precise dissociation