Wetlands store carbon in vegetation and soils, while also emitting greenhouse gases such as methane and nitrous oxide. However, there is a lack of research on estimation of greenhouse gas emissions from wetlands, leading to high uncertainty and low accuracy of quantification in national greenhouse gas inventories. To improve the accuracy of assessment, it is necessary to develop country-specific emission factors that account for unique environments. This study aimed to propose a classification system for wetlands and establish an emission factor development plan. We assessed wetlands based on wetland type (vegetation, bare ground, agricultural land, water body, etc.) using data from the 4th General Survey on National Inland Wetlands (2020) and Basic Survey on Inland Wetlands (2022). We also identified a methodology for quantifying emissions in wetlands by reviewing the IPCC guidelines. Furthermore, we analyzed national inventory reports (NIRs) from major Annex I countries to evaluate the current tier levels and the application of emission factors. We proposed classification system based on the presence of water and vegetation. Also, we established goals for developing country-specific emission factors and described the data required for the development process. These findings will contribute to the development of a framework for accurate and reliable estimation of greenhouse gas inventories in wetlands for governments and other management agencies.