Plots were set up in typical hilly red soil region field (conventional tillage, CT and no tillage, NT) of central Hunan province. Simulated rainfall experiments were conducted to modify the built linear regression model in which the variable was the runoff rate of sediment delivery by runoff, and then, the model of SOC loss was established on the basis of the revised model and SOC enrichment characteristics of sediment. The results showed that the model of SOC loss could be effectively adapted to the simulation of SOC loss in hilly red soil region of central Hunan province during a rainfall event and could get a wonderful simulation result and accuracy. The mean error from the simulation of SOC loss rate was observed to be around 30% with the determination coefficient beyond 0.85 in CT and NT. In the meantime, the simulated results indicated that the process of the sediment and SOC loss revealed a fluctuant state under overland flow erosion. The sediment and SOC loss rate rose at the first stage of 0~10 min after runoff began and then kept a relatively stable tendency. Comparing the model of sediment transport by runoff and SOC loss in NT with that in CT,the results demonstrated that the sediment and SOC loss rate in CT were greater than that in NT under erosive rainfall. And the situation of sediment and SOC loss in CT were similar to that in NT under non-erosive rainfall.