Abstract: In order to study the relationship between erosion and sediment yield in slope and gully, the hydraulic characteristics of runoff in slope-gully systems were studied in this paper by dual slope segment combination model, through the indoor scouring test, combined with REE tracer technique. The results showed that the changes of runoff Reynolds number (Re) in the slope-gully systems was located between 342.3 and 858.8, and the magnitude of changes increased with the increasing of erosion lasted time in the range of experimental flow. The changes of Froude number (Fr) in the slope-gully systems was varied between 1.36 and 8.92, and it had a spatial and temporal variation characteristic in the range of experimental flow. The runoff velocity of slope in slope-gully systems first increased then decreased under the condition of the same flow. The flow velocity reached a minimum value when runoff transition from slope to gully. It began to increase again after flow into gully. Darcy-Weisbach drag coefficient and Manning roughness coefficient firstly decreased, then increased and then decreased with test section from top to bottom in the same flow. The study can provide a theoretical basis for foundation of erosion and sediment yield model of slope-gully systems in Loess Plateau.