[Objective] The hydraulic characteristics and ¹³C isotopic characteristics of the non-uniform enrichment of light (LF_OC) and heavy (HF_OC) fractions of soil organic carbon in sediments during the sheet erosion process were determined in order to provide theoretical and technical support for a better understanding of the dynamic changes in soil organic carbon stocks under water erosion.[Methods] This study was conducted on Lou soil from Yangling District of Xianyang City, Shannxi Province. An improved "three-zone" mobile steel soil pan was used together with an artificial rainfall simulator to measure runoff hydraulic parameters, organic carbon compositions of each aggregate size in sediments, and their related δ¹³C values. Additionally, these results for Lou soil were verified based on the δ¹³C values of organic carbon in eroded sediments and runoff hydraulic parameters for brown soil.[Results] ① When rainfall intensity and slope were low, both LF_OC and HF_OC were enriched in eroded sediments, and the organic carbon composition of macroaggregates were observed to be more susceptible to the influence of rainfall intensity and slope than observed for clay and silt particles and microaggregates. ② The δ¹³C values of organic carbon in clay and silt particles were negatively correlated with the percentage of LF_OC in SOC (λ), while the δ¹³C values of organic carbon in other size aggregates showed a significant positive correlation with λ values (p<0.05). ③ Flow velocity was positively correlated with λ values of clay and silt particles (p<0.05), while Reynolds number was negatively correlated with δ¹³C values of clay and silt particles, microaggregates, and macroaggregates (p<0.01). Increasing flow velocity during sheet erosion promoted the preferential transport of clay and silt size organic carbon, while turbulence promoted the transport of organic carbon with low δ¹³C values in aggregates; ④ For clay and silt particles, the larger the flow velocity and Reynolds number, the smaller the δ¹³C value of organic carbon and the larger the λ were. For microaggregates and macroaggregates, the smaller of Reynolds number, the larger the δ¹³C values of organic carbon and λ values in microaggregates were.[Conclusion] The loss of LF_OC and HF_OC was closely related to flow velocity and Reynolds number during the sheet erosion process. The effectiveness of using the ¹³C isotope in tracing organic carbon in eroded sediments was verified.