To investigate the effects of herbs'root systems on soil water properties,the root systems of vetiver〔Vetiveria zizanioides(Lin.)Nash〕，bahia grass(Paspalum natatum),bermuda grass〔Cynodon dactylon(L.)Pers.〕and alfalfa(Medicago sativa L.)were scanned by WinRHIZO,and the correlations between these root systems and soil physical properties and soil water holding capacity were analyzed bySPSS18.0.Results showed that the root length density of herbs decreased as soil depth increased,which canbe simulated by an exponential function.Roots of vetiver and alfalfa were mainly distributed in the 0-20cmsoil layer,but roots of bahia grass and bermuda grass were concentrated in the 0-10cm soil layer.Soil porosity,non-capillary porosity,water capacity and saturated water holding capacity decreased,but soil bulkdensity increased as soil depth increased.The improvement of soil moisture was mainly realized by roots ofdiameters in the ranges of 0.5mm