To elucidate the roles of angle between rock and slope in affecting the processes of runoff and sediment yield in the Karst Trough Valley Area of Southwest China, the combined conditions of 6 angles between rock and slope (30°, 60°, 90°, 120°, 150°, 180°), 3 slope gradients (10°, 15°, 20°), and 3 flow rates (5, 7.5, 10 L/min) were employed in laboratory scouring simulation experiments. Results showed that:(1) Surface runoff rate increased to be stable with scouring duration, while sediment concentration and sediment yield rate both increased first and then decreased with the scouring duration; (2) Surface runoff rate showed non-significant differences among different angles between rock and slope (P>0.05). Sediment concentration and sediment yield both displayed non-significant differences among the angels of 30°, 60° and 120° (P>0.05),which were significant higher than those angels of 90°, 150° and 180° (P<0.05); (3) Surface runoff rate presented significantly positive power relationships with sediment concentration under the angles of 60°, 90° and 120° (R²=0.32~0.56, P<0.05), while exhibited non-significant relationships with sediment concentration at other angles (P>0.05). Similarly, surface runoff rate was significantly linearly correlated with sediment yield at the angles of 60°, 90°, 120°, 150° and 180° (R²=0.35~0.86, P<0.05). Our results show that a certain angle between rock and slope in the slope of the Karst Trough Valley area can accelerate the sediment yield and change the relationship between runoff and sediment yield.