[Objective] The law of soil organic carbon (SOC) differentiation and its influencing factors in small hilly and mountainous catchment areas was studied to provide a scientific basis for the sustainable utilization of soil resources and the protection of water sources of the South-to-North water diversion project.[Methods] The spatial and temporal distribution and influencing factors of SOC in the Jianghe watershed, Shiyan City, Hubei Province were analyzed, based on the digital elevation models (DEM), Landsat 8 OLI products, and measured SOC data from 2016 to 2018. These were analyzed using a correlation analysis and principal component analysis methods.[Results] Regarding the spatial distribution, the SOC had a banded distribution and the concentration of SOC in northeast of the watershed was smaller than that in the southwest. The variability of the SOC was of a middle intensity. The SOC concentration decreased in summer and autumn, whereas it accumulated in winter. For different soil types, the SOC concentration exhibited the following order: calcaric fluvisols > haplic luvisols > dystric cambisols. For different landcover types, the SOC concentration exhibited the following order: farmland > garden plot > mixed forest > evergreen coniferous forest > deciduous shrubs. The SOC increased along with the absolute value of the earth's surface curvature and the values of ratio vegetation index (RVI) and normalized difference vegetation index (NDVI).[Conclusion] The topographic factor is the main influencing factor of SOC concentrations in the Jianghe watershed, and vegetation factors (RVI and NDVI) were the second principal components for the SOC variation. The SOC concentration can be increased by changing local small landforms, increasing forest species, and improving water and fertilizer management.