The hydraulic characteristics of rill erosion were studied by using runoff scouring experiment under the different steep Loess slope gradients(25°,30°,35°,40°,45°,50°) and the different flow discharges(0.6,1.0,1.5,2.0,2.5 L/min). The results showed that velocity decreased first,then kept smooth and steady as the scouring time. The Reynolds number of the flow varied between 199.996 and 873.482 in the erosion process. It was affected mainly by the flow discharge which was in a linear relationship with flow discharge. The Froude number of flow was larger than 1 in the whole experiments,which indicated that the rill flow belonged to the supercritical flow condition. Meanwhile,the Froude number of rill flow was in a reciprocal decreased relationship with flow. Darcy-weisbach resistance coefficient (f) was positively related to flow and was in a power function relationship with the Reynolds number.