As one of the important parameters, sediment transport capacity must be considered when developing physical models of soil erosion. It is necessary to research on the concentrate flow sediment transport capacity for a better understanding of rill erosion mechanism and for control purpose. An indoor concentrate scouring experiment was carried out to investigate the concentrate flow sediment transport capacity under different flow rates and slopes. Loessal soil, a kind of typical soil in the Loess Plateau, was prepared for this research. The relations between sediment transport capacity and inflow rate, slope were analyzed, the regression of sediment transport capacity with inflow rate and slope and with unit discharge per unit width and slope were established, and the relations between runoff hydrodynamic characteristics and sediment transport capacity were also analyzed. The results indicated sediment transport capacity increased with the increasing inflow rate and slope. Multivariate power function regression of sediment transport capacity with inflow rate and slope indicated slope was more influential on sediment transport capacity than that of inflow rate. However, unit discharge per unit width was more influential on sediment transport capacity than that of slope because of the flow convergence under steep slope. In general, all of runoff hydrodynamic characteristics can describe sediment transport capacity well, and the optimal factor in our research was stream power as it had the largest determination coefficient. The results provide valuable information for a better understanding of the sediment transport capacity in concentrate flow on loess hillslope.