Abstract: Two sampling lines from oasis to desert and to dune were chosen,each with four observation points,to observe wind velocity and silt discharge rate synchronously.The data of two years showed that fore-protective forest of oasis-desert played an important role in decreasing wind velocity.As for the species,taking their growth rate and drought resistance into account,the combination of Populus simonii and Tamarix ramosissima was the most ideal fore-protective forest.Without arbor and shrubbery,the grass sand-fixing area could not reduce the wind velocity further.In the protective forest from oasis to dune,the slit discharge rate increased significantly with the decrease of ground surface coverage,which meant that the increase of ground surface coverage is the key to decrease the silt discharge rate.

Key words: Loess Plateau, Grassland, Bare land, Soil water, Cycling