As newly artificial landform, soil erosion of spoil heaps severely threatens the ecological security of construction sites and their surrounding areas. Generally, rill erosion is recognized as an important process of soil erosion on spoil heaps slope. However, studies on spoil heaps rill erosion characteristics and its intrinsic mechanisms are still unclear. The objectives of this study were to investigate the rill morphological characteristics, rill flow hydraulic characteristic and dynamic mechanisms. A field runoff plot (10 m long, 1 m wide and 0.5 m deep) was subjected to inflow simulation experiments under flour flow discharges rates (5, 9, 13 and 17 L min⁻¹) and three typical slope gradients (24°, 28° and 32°). The results showed that the rill erosion process could be divided into two stages: a rapid development stage (RDS) and a subsequent slow development stage (SDS). Among that, the rill width, rill depth, cumulative runoff yield and cumulative sediment yield in RDS average accounts for 81 %, 57 %, 29 % and 41 % of the total, respectively, which indicated that the rill depth exhibited significant contributions to spoil heaps rill erosion. The flow regimes in the RDS were turbulent, transitional and laminar flow, whereas in the SDS was transitional flow. The flow type in the RDS was supercritical flow, whereas in the SDS were supercritical flow and subcritical flow. For the whole erosion process (including two stages), the critical shear stress and the critical runoff power were 10.00 Pa and 3.22 N m^-1 s^-1, respectively. Furthermore, runoff power could be considered as the best hydrodynamic parameters to characterize the rill erosion mechanism. These results could be used to control artificial erosion caused by production and construction projects and to provide some key indicators for soil and water loss perdition in Loess Plateau of China.