[Background] In the early last century, the problem of soil erosion has been quite serious, thus it is urgent to carry out scientific and effective soil and water conservation work for preventing soil erosion. China is a country with one of the most serious soil erosion, the Loess Plateau is the most serious soil erosion area in the world, and it is also the main source of the Yellow River sediment area; the Loess Plateau region of soil erosion cause not only the deterioration of ecological environment, but also a serious threat to the lower reaches of the Yellow River ecological security. [Methods] In order to explore the hydrodynamics characteristics of rill flow, the dynamics characteristics of rill flow from the perspective of hydraulics and rivers movement mechanics were studied under the combined scouring test condition of 6 slopes (2°, 4°, 6°, 8°, 10°, and 12°) and 5 discharges (8, 16, 24, 32, and 40 L/ min). [Results] Results indicated that the average velocity of rill flow was in power function relationship with discharge.However, the there was no correlation between the velocity and slope, which was because the development of drop pits was more mature with the increase of the slope, resulting in the growth of rill flow path. The thickness of the viscous sub-layer was in negative correlation with slope and discharge, and presented an essential effect on rill flow resistance. Resistance coefficient varied from 0.16 to 1.45 and increased with the increase of the slope and showed no correlation with Reynolds number, meaning that the flow regime belonged to the turbulent rough area, this was because the morphology of bed surface developed significantly, i. e. , the dissipation capacity of the flow increased significantly, with the increase of the intensity of rill flow. [Conclusions] The experimental results showed that the bed morphology of loess slope had great influence on the velocity of rill flow. By reasonably changing the bed morphology of loess slope, the flow velocity can be decreased and onsequently the soil erosion on the Loess Plateau region can be controlled. In this experiment, the height of bed surface bump was several times higher than the viscous sub-layer because the thickness of viscous sub-layer was thin. The resistance resulted from the small vortexes formed while turbulent flow was bypassing the bump. The result of this study has certain theoretical value to the exploration of the dynamics of rill flow, and has certain guiding significance to control the soil erosion on loess slope and to restore eco-environment.