Runoff, sediment yield and infiltration process of shrub plots were studied under rainfall intensities of 45, 87 and 127 mm/h with 20° slope gradient using simulated rainfall experiment. The results showed that cumulative runoff and cumulative sediment yield of shrub plot had an obvious positive correlation with rainfall time. Under rainfall intensity of 45 mm/h, runoff and sediment yield of shrub plot kept a constant level. Under rainfall intensity of 87 mm/h, runoff kept a fluctuant increase, whereas sediment yield basically kept steady. Under rainfall intensity of 127 mm/h, runoff and sediment yield of shrub plot increased evidently due to the formation of erosion pits. Infiltration rate of shrub plot had a negative relation with runoff as well as sediment yield.

Simulate rain experiment method was adopted to study the transformation of the change of raindrop speed and diameter with time and the results indicated that the rain intensity change strongly with time at the natural rainfall, However, the rain intensity was stability at simulate rainfall. At the natural rain, the raindrop speed mainly at 0.4-6.6m/s in different time, it have two wave crest were 1m/s and 3.4m/s. However, at the simulate rain, the raindrop speed mainly at 0.2-5.8m/s in different time; it has one wave crest was1m/s.In natural rain and simulate rain, the 0.125mm diameter raindrop speed were about at 0.4-2.6m/s and0.8-5.8m/s, the 0.25mm diameter raindrop speed was about at 0.6-2.6m/s and 0.6-5.8m/s, the 0.375mm diameter raindrop speed was about at 1-1.8m/s and0.4-2.2m/s, the 0.5mm diameter raindrop speed was about at 1-3.4m/s and 0.2-1.8m/s, the 0.75mm diameter raindrop speed was about at 3.4-4.2m/s and1-3.4m/s, the 1mm diameter raindrop speed was about at 3.4-4.2m/s and 1-3.4m/s, the 1.25mm diameter raindrop speed was about at4.2-5m/s and1-5m/s, the 1.5mm diameter raindrop speed was about at5m/s and 2.6m/s.

Effect of shrub on runoff and sediment yield and its hydraulic mechanism of shrub were studied under rainfall intensities of 45, 87 and 127mm/h with 20°slope gradient using simulated rainfall experiment. the results showed that average runoff rates ranged from 39.7 to 126.0 L/min for bare plots and 0.77 to 4.83 L/min for shrub plots, and the runoff rates from shrub plots were much less than from bare plots. Average sediment yields varied from 3636.7 to 9436.3 g/min for bare plots and from 28.0 to 421.6 g/min for shrub plots. The critical flow shear stress of 1.65 N/m2 on shrub slope and 0.861 N/m2 on bare slope were got under experiment condition. The sediment yield increased with the increase of flow shear stress. The experiment results are meaningful for quantifying runoff and sediment reduction and deepening soil erosion mechanical process also.