Abstract: Wetlands are known as one of the natural ecosystems with the highest carbon density. The analysis of the spatial distribution characteristics of soil organic carbon in wetlands is of significant importance to the formulation of effective conservation and management policies. Our study employed comprehensive field investigations and sample collections to quantify the soil organic carbon content and density at different slope positions (low, middle, and high) across 13 monitoring sections along the Yongding River in Mentougou. This study aimed to elucidate the spatial distribution characteristics and primary influencing factors that determine soil organic carbon in the riparian wetlands of the Yongding River in Mentougou. The results show that the soil organic carbon content in the riparian wetland ranged from 2.25 to 88.67 g·kg^-1, with an average of 17.87 g·kg^-1, and the organic carbon density ranged from 2.14 to 19.13 kg·m^-2, with an average of 7.59 kg·m^-2. Notably, the soil organic carbon density exhibited an initial increase followed by a subsequent decrease along the river′s runoff direction. Furthermore, the canyon sections displayed significantly higher soil organic carbon density compared to the plain sections. In the vertical riparian zones, soil organic carbon density decreased gradually from the low riparian zone to the high riparian zone. There is a significant positive correlation between soil organic carbon content and density and soil moisture content in the Yongding River riparian wetland. This study provides valuable data to support the protection and management policy of the Yongding River wetland in Mentougou.