【Objective】Hydraulic characteristics of shallow flow are essential to elucidating mechanisms of soil erosion and sediment yield on the slope. However, most of the studies in this aspect have been reported on slopes less than 25° in gradient. This paper is oriented to study hydraulic characteristics of steep loess slopes (25°~50°), in an attempt to lay down a foundation for elucidating in-depth relationships of the hydraulic characteristics of shallow water flow on slopes with slope soil erosion. 【Method】An indoor experiment was carried out simulating rainfalls on steep loess slopes. The experiment was designed to have only one soil type (loessal soil), three rainfall intensity (1.0mm min-1, 1.5 mm min^-1 and 2.0 mm min^-1) and six slope gradient (25°, 30°, 35°, 40°, 45° and 50°) with the aid of perforated metal flumes (3 m in length, 1 m in width and 0.30 m in depth). Runoff, sediment and flow velocity on the slopes were observed, relative to rainfall intensity and slope gradient. 【Result】Results show: (1) Flow velocity increased with rising rainfall intensity on slopes the same in gradient, and under the same rainfall intensity, the effect of slope gradient on flow velocity exhibited a critical point in gradient, that is, between 40° and 45° under the same rainfall intensity. On slopes with gradient lower than the critical point, flow velocity increased with rising slope gradient, whereas on slopes with gradient higher than the point, flow velocity decreased with rising slope gradient. (2) Mean runoff depth increased steadily with rising rainfall intensity on all slopes regardless of gradient; but decreased with rising slope gradient under rainfalls the same in intensity. (3) Reynolds numbers of steep loess slopes were on the whole relatively small, often far below 580. In this study shallow flows on slopes were of laminar flow in destabilized layers, while shallow flows with Froude number beyond 0.8 were of rush. And (4) Darcy-Weisbach resistance coefficient (f) was positively related to rainfall intensity and negatively to slope gradient. 【Conclusion】Rainfall intensity, slope gradient and interactions between these two factors all have significant effects on hydrodynamic parameters (p<0.01) of shallow flow on steep slopes, but flow velocity, Froude number and Darcy-Weisbach resistance of the shallow flow varied mainly with slope gradient, while runoff depth and Reynolds number did mainly with rainfall intensity.