Through plot-scaled field rainfall simulation experiments, effects of water erosion on transportation of soil organic carbon on a slope were analyzed. Results show that after 30 minutes of rainfall, the total sediment-associated loss of organic carbon was 56.09 g and 3.18 g, respectively, and the total runoff-associated loss of organic carbon was 13.55 g and 2.81 g from a plot 2 m × 5 m in size. Intensity and duration of rainfalls had significant effects on the process of soil organic carbon loss. The higher the rainfall intensity, the quicker and the more organic carbon was lost with sediment and runoff. In the initial 18 minutes of runoff triggered by rainfall of high intensity, the organic carbon enrichment ratio (ERsoc) of the sediment is higher than 1, and afterwards it dropped below 1, while throughout the rainfall event low in intensity it remained below 1. During the rainfall event high in intensity, a cubic regression relationship was observed between concentration of soil organic carbon in runoff and volume of the runoff, and the concentration of organic carbon in sediment was related to volume of the sediment, showing an obvious cubic relationship. For the low intensity rainfall, a linear relationship appeared demonstrating a rising trend of organic carbon loss with volume of the runoff.