Distribution of plant roots in a red soil derived from granite was investigated to study the effect of plant roots on intensifying soil penetrability and anti-scouribility by the double-cutting-ring and the undisturbed soil-flume methods, respectively. The plant roots system consisting mostly of fibrils, ＜ 1 mm in diameter,was mainly distributed in the upper surface soil 30 cm in depth. It can remarkably increase the penetrability and anti-scouribility of the red soil derived from granite. When the root density was ＞ 0.35 root cm-2, the intensifying effect of roots on both the penetrability and the anti-scouribility could be described by exponent equations, △Ks = 0.0021RD1.4826 (R2 = 0.9313) and △As = 0.0003RD1.8478 (R2 = 0.9619), where △Ks is the value of intensified soil penetrability, △ As the value of intensified soil anti-scouribility and RD the root density, especially in the top soils within 30 cm in depth where plant roots were concentrated.