【Objective】 A karst valley has not only surface/underground double-layered structure, but also two special geological structures, bedding slope and reverse slope. During rainstorms, bedrocks seem to form a discontinuous impermeable area, which reduces soil and water loss. Although it seems obvious that rock layer inclination influences hydrology in karst areas, little has been reported in the literature on this subject. Therefore it is of great importance to launch a study on rules of water transport with runoff in Karst Valley areas. So the objective of this study is to investigate roles of rock layer inclination in guiding surface water flow on slopes in karst valleys. 【Method】 Based on field investigations, a simulated rainfall experiment, designed to have bedding/reverse slopes (30°, 60° and 90° in gradient), 3 levels of rainfall intensity (30, 60 and 90 mm h^-1) and a bare slope as CK, was carried out on a slope approximate to the critical gradient (25°) of the nearby karst valley to explore runoff rate and hydrodynamic parameters and their relationships with bedding/reverse slopes. A total of 18 treatments and 3 duplicates for each were laid out and conducted in the experiment. The characteristics of soil hydraulics measured included flow velocity, Reynolds number (R_e), Froude number (F_r), Darcy-Weisbach roughness coefficient (f), and surface/underground accumulated runoff.【Result】Results show that with the rainfall experiment going on, runoff on the bedding slopes and inverse slopes was dominated with shallow watersplash. Over on bedding slopes, the overland flow slowed down in velocity, with rising inclination angle of the rock layer, while on reverse slopes the inclination angle of 60° was the threshold. Surface runoff flew faster on the bare slope than on bedding slopes and reverse slopes. Reynolds number (R_e) and Froude number (F_r) was higher on bedding slopes than on reverse slopes, but lower than on bare slopes, Darcy-Weisbach roughness coefficient (f) was lower on bedding slopes than on reverse slopes but higher than on bare slope. Value for Froude number (F_r) indicated that the water flow was a subcritical one, and was generally higher on bare slopes than on bedding slopes and reverse slopes. Darcy-Weisbach roughness coefficient (f) was much lower on bare slopes than on bedding slopes and ireverse slopes, showing order of reverse slope ＞ bedding slope ＞ bare slope, and decreased with increasing Reynolds number (R_e), which was in an extremely significant positive power relationship with Reynolds number (R_e). Accumulated surface runoff varied with rock layer inclination in the order of bare slope ＞ bedding slope ＞ reverse slope , while accumulated underground runoff followed an order of reverse slope ＞ bare slope ＞ bedding slope.【Conclusion】Overall, the findings may provide certain data support for analysis of the mechanism of runoff generation and scientific basis for further research on processes of the runoff and models of the soil erosion in karst valley areas. Meanwhile, these findings are expected to be of some help for building prediction models for soil erosions in similar environments different in rock layer inclination.