Abstract <p>The autumn freeze-thaw period plays a critical role in regulating soil carbon dynamics in permafrost region. However, the dynamics of soil carbon dioxide (CO₂) and methane (CH₄) fluxes during the autumn freeze-thaw period in high latitude permafrost regions of China remain poorly understood. In our study, we measured soil CO₂ and CH₄ fluxes using the dark chamber method in three different stand ages of birch (<i>Betula platyphylla</i> Sukaczev) forests (30, 45, and 66 years old) in the Daxing’an Mountains permafrost region and explored their relationships with key soil factors. Mean soil CO₂ and CH₄ fluxes are 19.24 to 36.44&#xa0;mg m^–2 h^–1 and –12.22 to –25.92 μg m^–2 h^–1, respectively during the study period. Both soil fluxes in 30 years forest stand were significantly lower than in the older stands (45 and 66 years, <i>P &lt;</i> 0.05). Across stand ages, soil CO₂ fluxes were strongly driven by soil temperature and dissolved organic carbon, whereas CH₄ fluxes were jointly regulated by soil temperature and volumetric water content. These findings highlight the critical but underappreciated role of soil CO₂ and CH₄ dynamics during the autumn freeze-thaw period in permafrost carbon feedbacks, underscoring the need to explicitly include this period for ecosystem carbon budget in permafrost regions, especially under climate warming background.</p>