In this paper, a mathematical model of water exchange for hillslope, with which hysteresis was incorporated, was presented. The solution conditions of various boundary conditions were analyzed in this model. At the same time, the model was proved systematically by using the natural rainfall-infiltration-runoff data of hillslope of Wangdong gully small watershed, Changwu in Shaanxi. The simulated results showed that the model was of high precision, especially when the hysteresis was considered, the predicted results were approximated to measured results. Hysteresis results in decreasing in water content in the wetting front measured at the end of infiltration, slows down the redistribution. During the process of rainfall-infiltration-runoff,hysteresis has a great effect on water content, infiltration rate, flow process and flow volume.