Large-scale closure of coal mines is required for China to achieve carbon neutrality. However, what this means for methane emissions, particularly for abandoned mine methane (AMM), is highly uncertain. Here we construct a detailed and dynamic coal mine database to estimate China’s coal methane emissions during 2011–2019 and evaluate future emission trajectories based on different mine closure policies. We find that AMM emissions have been largely underestimated, which leads to an increased proportion of AMM in China’s total coal methane emissions, and are expected to become the dominant source by 2035. We develop a coal mine closure strategy prioritizing high-gas-content mines. Compared with the current closure strategy based on mine scale, this strategy could reduce cumulative methane emissions by 67 Tg (26%) to 2050, potentially reaching 100 Tg (39%) with improved methane recovery and utilization practices.