The simulated rainfall experiment was conducted on three different land types, i. e. , Vetiveria zizanioides L. , ordinary grass and bare land, to analyze water and soil conservation effects and mechanism of V. zizanioides contour hedge. The results of a series of experiments showed that, compared with bare land, the V. zizanioides hedgerow reduced runoff by 21%, while the sediment yield was only 18% of that on bare land. The initial time-to-runoff of V. zizanioides contour hedge lagged behind prominently. With the rainfall intensity increasing, the effect of reducing runoff and sediment was more significant. The effect of reducing runoff and soil erosion was controlled by developed root system which improved soil structure, maintained higher water infiltration capacity, and thus reduced surface runoff. The huge aboveground biomass weakened the kinetic energy of raindrops, and reduced their impact on soil particles.