Abstract: Hystersis influences infiltration characteristics and runoff volume during the process of rainfall infiltration runoff. However, the study on the hystersis mechanism and model in rainfall infiltration runoff is not reported now. In this paper, a model of rainfall infiltration runoff for hillslope, which hystersis was incorporated, was presented by analyzing the hystersis mechanism. The model was proved systematically by using the natural rainfall infiltration runoff data of hillslope at Wangdong gully small watershed , Changwu county in Shaanxi province. The simulated results showed that the model was of high precision, especially when the hystersis was considered, and predicted results were approximated to measured results. It is very necessary to consider the effects of hystersis during the process of rainfall infiltration runoff.