This study combines molecular dynamics simulations and quantum chemical calculations to investigate the evolution characteristics of gaseous products and the hydrogen generation pathways during the pyrolysis of polyvinyl chloride (PVC). Simulations under various temperature conditions reveal that H₂, CH₄, C₂H₄, and C₂H₂ are the main pyrolysis products, and their yields increase significantly with temperature (2000–3000 K). Based on bond energy analysis, the C–Cl bond is identified as the most susceptible to cleavage, which induces successive dehydrogenation reactions at the chain ends. Further construction of representative reaction pathways and energy barrier calculations indicate that the synergistic effect of C–C bond cleavage and β-position C–H elimination leads to H₂ formation, with activation energies of 345.7 and 398.8 kJ/mol for the two key steps, respectively. This mechanism reveals the primary source of H₂ during PVC pyrolysis and provides theoretical support for the microscopic understanding of the pyrolytic behavior of polymeric materials.