Abstract:The resistance coefficient is one of the hydrodynamic parameters of the slope surface and also is an important eigenvalue that reflects the hydraulic characteristics of the slope surface. In order to explore the variations of surface runoff resistance coefficient of grassland in loess region with different rainfall intensities (0.7, 1.0, 1.5, 2.0, 2.5 mm/min) and slope gradients (7°, 10°, 15°, 20°, 25°), indoor artificial rainfall simulation was adopted in this study. The results showed that:(1) The sheet flow resistance coefficient of grassland slopes decrease firstly, and then gradually stabilized with the rainfall duration under different rainfall intensities and slope gradients. The relationship between resistance coefficient and rainfall duration could be described by a quadratic polynomial equation, and the correlation was significant, also the coefficient of determination was above 0.5. (2) The sheet flow resistance coefficient of grassland slope increased gradually with rainfall intensity, and the relationship could be described by a exponential equation with the coefficient of determination was above 0.8; while the sheet flow resistance coefficient of grassland slope decreased with the increase of slope gradient, and the relationship could be described by a logarithmic equation with the coefficient of determination was above 0.6. (3) The integrated response of the average flow resistance coefficient of the grassland slope could be described by a binary exponential function with the coefficient of determination was 0.923. Through comparative analysis, it was found that the influence of rainfall intensity to average sheet flow resistance coefficient was greater than that of slope gradient. This study provides a theoretical basis for the reference of grassland flow hydrodynamics and the flow control mechanism of grassland vegetation. It is of great significance for us to deeply understanding the erosion dynamics of grass slope and ecological construction in the loess area.