In this study, simulated rainfall was conducted to mainly investigate and analyze organic carbon content of sediment and its dynamic change during the rainfall on the outdoor runoff plot under random conditions. The sediment organic carbon content, which was significantly higher than that of the soil organic carbon (p＜0.01), decreased gradually during the early stage of the rainfall, then tended to be stable in the later stage. The organic carbon was obviously enriched in sediment, and the maximum of enrichment ratio was 1.780. The content and enrichment ratio of organic carbon in sediment decreased obviously with the increasing of erosion rate, and tended to be stable. The loss process of sediment organic carbon showed a unimodal distribution during the rainfall, which increased first with the rainfall, then decreased after reaching the maximum value, and finally tended to quasi stable. There was a significant linear relationship between soil organic carbon loss and soil erosion amount (p＜0.01), indicating that soil erosion amount determined the organic carbon loss during the erosion process, so accurate estimation of soil erosion intensity was the basis of estimating organic carbon loss on the slope.