This study aimed to analyze the spatial distribution of soil particle size and its relationship with environmental factors in the inland wetlands of the Hangang River Region, as well as to classify sandy soil based on IPCC guidelines for soil carbon stock evaluation. Soil data were collected from 250 survey sites, and the Random Forest algorithm was used to predict the spatial distribution of sand and clay content, which served as the basis for sandy soil. The analysis revealed that elevation and mean elevation derived from the Korean Reach File (KRF) were the most influential factors to soil particle size distribution, with sandy soil predominantly concentrated in the upper reaches of the Hangang River. The estimated carbon stock in sandy soil within inland wetlands was about 1.247 million tons, highlighting the need for further refinement of accumulation coefficients tailored to domestic conditions. This study is expected to contribute to the development of a national greenhouse gas inventory by providing soil data for inland wetlands.