Based on the studies on the profile characteristicts of root density, root weight and soil anti-scouribility, the sidement reduction effect of herb roots and the range of soil anti-scouribility increased by herb roots distributed in different soil layers are first quantitatively analyzed. The results obtained show that the intensified value of soil anti-scouribility by the roots was more closely correlated with the root density than with the root weight. Within top 20 cm soil layer, the effeu of sidement reduction was not influenced by slope and rainfall intensity. This effect, however, was evidently weakened with the increase in profile depth. According to the comprehensive analyses of the effect curves of herb roots to increase soil antiscourbility and sediment reduction effects under conditions of different slopes(150,200 and 300) and rainfall intensities (0.5, 2.0 and 4.0 mm/min), the density range and lower depth limit of herb rotxs to obviously increase soil ati-scouribility are proposed.