[Objective] The slope flow velocity in abandoned dreg site and the effects of gravel content, slope gradient, water flows discharge, and sediment concentration on it were demonstrated to provide scientific reference for revealing the erosion mechanism on dreg site. [Methods] Field scouring experiment was carried out to study the velocity of residue slop in Shenfu Coalfield. [Results] Results showed that flow velocity experienced fluctuated processes within a certain range on all flow discharge conditions. The velocity along discharge time was multi-valley multimodal, and its fluctuation range observed in flow sections increased with the increase of discharge amount. Power function could be used to describe the relationships between flow velocity and the influence factors, including gravel content, flow discharge and sediment concentration. Quadratic power function could express the relationship between velocity and slope gradient. Stepwise regression analysis showed both flow discharge and gravel content significantly influenced flow velocity. [Conclusion] Variation of flow velocity on abandoned dreg slope was complicated. Gravel amount and upstream catchment area were two key factors influencing flow velocity.