<p>Methane (CH₄) is a highly potent greenhouse gas due to its high radiative forcing and global warming potential. Understanding the magnitude, spatial patterns, and drivers of CH₄ emission from wetlands at the regional scale is crucial for formulating suitable strategies to mitigate future climate change. In this study, we synthesized the CH₄ flux data reported for major plant communities in the coastal salt marshes and mangrove forests in China and produced a spatial map of CH₄ fluxes from the mangrove sediments and salt marshes in China based on the results of machine learning models. Moreover, we examined the main drivers of CH₄ flux from these coastal wetlands and estimated the annual CH₄ emissions from the salt marshes and mangrove forests in different coastal provinces of China using a bottom-up approach. Our results showed that the mean CH₄ fluxes from the salt marsh and mangrove ecosystems in China were 2.22±0.29 and 2.26±0.55 mg m⁻² h⁻¹, respectively. Across China, the total annual CH₄ emission from salt marshes was 31,179.75 Mg CH₄ a⁻¹, while that from mangroves was 5,533.97 Mg CH₄ a⁻¹ with the sediments contributing to 12.7% (701.64 Mg CH₄ a⁻¹) of the total efflux. The salt marshes and mangroves in China accounted for 2.75% and 0.14%–0.15% of the global annual CH₄ emissions from these two ecosystems, respectively. Moreover, we found that CH₄ emissions from the salt marshes and mangroves could offset the cooling impact arising from net carbon dioxide uptake by 88% and 53%, respectively, over a 100-year time scale. Mean annual temperature, soil moisture, and soil organic carbon content were the main factors controlling CH₄ emissions from these coastal wetlands. Furthermore, we found that CH₄ fluxes from the salt marshes in China decreased with latitude, which implied a possible increase in marsh CH₄ emission in response to global warming that should be considered carefully when developing nature-based climate solutions to achieve national goals for carbon neutrality.</p>