The "flexible dam" made of the Seabuckthorn plant is a new bio-engineering measure used in soil erosion controlling,sediment retention and water conservation in gully,especially in the soft rock region with serious environmental problems.A field experimental research on sediment retention and water conservation by the seabuckthorn plant "flexible dam" was carried on in the small East-One-Branch gully in the representative soft rock region of Zhungeer County,Erdos City,Inner Mongolia.The analyses of sediment particle distribution and monitored and measured soil moisture data obviously show that the "flexible dams" are mostly silted up.Sediment in gully channel is subject to a natural selection-intercepting coarse sediment particles and depositing fine sediment particles by using the "flexible dams" together with small rigid dams down stream of gully channel.Much of the sediment is just held up in gully and the effect of sediment retention is very distinct.The "flexible dam" can strikingly regulate soil water in gully channel,and the dynamic change in the distribution of soil water in soil profile is obviously different in different positions of the "flexible dam" each year.The seabuckthorn plant "flexible dam" can improve the effects of conserving water,boost the self-reproducibility of "flexible dam" and achieve the self-growth of it.