Abstract: The observed data of hillslope under natural rainfall-infiltration-runoff condition on small watershed in Loess Plateau are simulated by the models considered and unconsidered hysteresis, respectively.The simulated results shows that the hysteresis increases the infiltration rate and reduces the runoff volume during the process of rainfall-infiltration-runoff.The predicted soil water content and runoff volume are approximate to the measured values.From this, we know that the hysteresis has a considerable influence on soil moisture, infiltration rate, runoff process and runoff volume.It is very necessary to consider the effects of hysteresis in the study on water exchange in the future.