The slope erosion and sediment yield are mainly affected by the dynamic process of slope runoff. The characteristics of slope runoff process are described by hydraulic parameters. The purpose of this paper was to study the relationships between slope erosion and sediment yield and hydraulics parameters，and to reveal the hydrodynamic mechanism of slope erosion and sediment yield through artificial rainfall simulation. The principles of classical hydraulic calculation and statistical fitting were applied for the comprehensive analysis of runoff and sediment yield process in different rainfall intensities and slope lengths. Five slope lengths (1

2

3

4

5 m) with 13 rainfall intensities were designed under a specific slope (20°). The conclusions were listed as follows: (1) Within the designed rainfall intensities (0.65～2.0 mm/min) and slope (20°)

slope surface runoff were slowly

which was laminar flow under rainfall intensity < 0.7 mm/min

the smallest rainfall intensity of turbulent flow occurrence was 1.01 mm/min. (2) The influence of the slope length on the Froude number and resistance coefficient were larger than on the shear stress

runoff depth and Reynolds number. The slope length of 3 m was the step length of slope runoff fluctuation

and was the shortest slope length designed for a simulated experiment of hydrodynamic parameters. (3) The velocity was the main influence parameter of slope surface erosion and sediment yield

and the shear stress was one of comprehensive indicators for estimating the strength of slope surface erosion and sediment yield. The above results provided a simple and rapid judgment method for predicting the intensity of erosion and sediment yield through runoff and flow velocity in wide field.