Abstract: Previous researches believe that water level fluctuations play a significant role in the influence of anthropogenic activities on soil organic carbon (SOC) in the riparian zone.However, the mechanism remains inadequately understood, especially the impact of terrestrial anthropogenic activities.The research aims to investigate the combined effects of periodic water level fluctuations in the Three Gorges Reservoir (TGR) and alterations in land use on various forms of SOC within the riparian zone.The physicochemical properties of soil samples collected from different riparian zones and elevations in the main and tributary rivers of TGR, as well as various forms of organic carbon, were analyzed.Analytical methods, including the Mantel test and random forest analysis were employed to identify the primary factors influencing the distribution characteristics of SOC in the riparian zone.The findings reveal that total nitrogen content in the soil is the most critical factor affecting SOC storage.Prolonged inundation duration positively influences soil physical properties while negatively impacts chemical properties, thereby indirectly regulating the storage of dissolved organic carbon (DOC) within the soil.Furthermore, the expansion of farmland and construction land facilitates the accumulation of soil recalcitrant organic carbon (ROC) but adversely affects DOC storage.Concurrently, an increase in total nitrogen content in the soil indirectly enhances the storage of soil DOC, microbial biomass carbon (MBC), and ROC.In contrast, the growth of farmland and construction land exerts a more pronounced positive effect on physical indicators and a more significant negative effect on chemical indicators compared to inundation duration, thereby indirectly influencing the distribution of soil DOC.Consequently, changes in farmland and construction land emerge as the most significant factors affecting the storage of various forms of SOC in the riparian zone, surpassing the impact of periodic water-level fluctuations.The results of the research provide key scientific evidences for the assessment of carbon dynamics in the riparian zone and the evaluation on its source-sink functions.