Abstract: Abstract: The change of runoff dynamics on the slope has a decisive effect on the erosion and sediment yield characteristics and erosion intensity. Runoff change is the essence of the hydrodynamic characteristics of soil erosion, runoff is the driving force and the carrier for erosion phenomenon, the change of the hydrodynamic parameters of slope surface flow can reveal some change law of slope runoff, and there is a close relationship between runoff and the hydrodynamic parameters. The deep understanding of the dynamic characteristics of the slope and its variation are the basis for understanding the soil erosion process and the dynamic mechanism of the slope, which is of great significance for the construction of the slope erosion prediction model. We conducted artificial simulated rainfall experiment in the State Key Laboratory of Eco-Hydraulic Engineering at Xi’an University of Technology in China from July to August 2013. We studied quantitatively the temporal and spatial distribution of hydrodynamic parameters on slope and its relationship with runoff and sediment yield under the same rainfall intensity (1.5 mm/min) and different sand-covered thickness (0.5, 1.0, 1.5 cm) in simulated rainfall in order to reveal the internal regularity of hydrodynamic parameters on slope. We also used potassium permanganate (KMnO4) to determinate the flow rate. Hydrodynamic parameters such as Reynolds number, Froude number, drag coefficient and Manning roughness were used to describe the hydrodynamic characteristics of sand-covered slope and its relationship with runoff and sediment yield. The results showed a fluctuating trend of temporal and spatial distribution of hydrodynamic parameters of the slope flow. As the surface roughness of the slope of the different layer of sand-covered thickness increased, the current flow state became fast and the flow rate increased. Compared with the bare slope, the Reynolds number increased by 39%-103% times, the number of Froude number increased by 5%-29% times, the f increased by 5%-155% times. In the process of rainfall, the sand-covered slope was mainly composed of laminar flow and turbulence flow. The rill development mainly in middle and later periods of the rainfall (runoff after 10 min) as well as between 1-10 sections (From the bottom of the slope, each 1m is divided into one section) after sand-covered, it had the obvious difference with the loess slope surface, namely loess slope surface rill formed mainly in runoff after 15 min, 1-8 sections (From the bottom of the slope, each 1m is divided into one section). The slope velocity and runoff depth of sand-covered slope were significantly (P<0.05) higher than the bare slope in the middle and later stages of runoff. The relationship between runoff and sediment yield on the slope and the hydrodynamic parameters could be described by simple linear regression. Reynolds number and relative depth Manning roughness can better describe the erosion process of sand-covered slope. The results provides data support for the analysis of the sediment yield mechanism and the sand-covered slope erosion production model and provides scientific basis for further researching the coupling mechanism of wind-water alternate erosions and environmental to erosion, and support to further study the effect of wind erosion of water erosion after sedimentation.