A new process-based model TRIPLEX-GHG was developed based on the Integrated Biosphere Simulator (IBIS), coupled with a new methane (CH<sub>4</sub>) biogeochemistry module (incorporating CH<sub>4</sub> production, oxidation, and transportation processes) and a water table module to investigate CH<sub>4</sub> emission processes and dynamics that occur in natural wetlands. Sensitivity analysis indicates that the most sensitive parameters to evaluate CH<sub>4</sub> emission processes from wetlands are <i>r</i> (defined as the CH<sub>4</sub> to CO<sub>2</sub> release ratio) and <i>Q</i><sub>10</sub> in the CH<sub>4</sub> production process. These two parameters were subsequently calibrated to data obtained from 19 sites collected from approximately 35 studies across different wetlands globally. Being heterogeneously spatially distributed, <i>r</i> ranged from 0.1 to 0.7 with a mean value of 0.23, and the <i>Q</i><sub>10</sub> for CH<sub>4</sub> production ranged from 1.6 to 4.5 with a mean value of 2.48. The model performed well when simulating magnitude and capturing temporal patterns in CH<sub>4</sub> emissions from natural wetlands. Results suggest that the model is able to be applied to different wetlands under varying conditions and is also applicable for global-scale simulations.