Biological soil crust plays an important role in degraded ecosystem restoration.Large area of biological crust has formed after cropland shifting to revegetated grassland on the hilly Loess Plateau of China. Our objective was to determine the impact of biological crust on soil chemical and physical properties in the study area.In this paper,through field investigation and sampling analysis,some physical and chemical properties of different years rehabilitated grasslands on the northern slopes which had biological soil crust formed on the surface were studied.Eight research sites were selected and soil and crust samples were collected in April 2004,with the restriction that locations were confined to a single soil series that was representative of the local environmental condition,similar elevation and slope.At each sampling site,five samples taken randomly were mixed to form a composite soil sample.Samples were taken from the 0 to 20 cm deep profile in 6 layers(crust,0-2,2-5,5-10,10-15 and 15-20cm).Soil moisture,bulk density,cohesion of soil surface,infiltration rate,organic matter content,total nitrogen,total phosphorus and available N,P,K contents of the 0-20cm soil profile were measured for soil samples taken from the 8 sites.The results showed soil physical and chemical properties of the 0-20cm profile were affected significantly by the biological crust.1)After shifting from cropland to revegetated grassland,soil moisture in the 0-20cm profile increased firstly and then decreased with the increase of rehabilitation years.Because the formation of the biological crust,soil penetrability of the rehabilitated grasslands reduced significantly compared with cropland,this also resulted in lower soil moisture in this profile after 10 years' rehabilitation.2)Soil surface cohesion of the rehabili-tated grassland increased significantly with the formation of the biological crust after shifting from cropland.After 10 years revegetation,the crusted soil surface cohesion of the revegetated grassland was 6 times that of the fresh revegetated grassland.The reason for this was mainly due to the formation of the biological crust,rather than the increase of soil bulk density.3)Soil penetrability reduced significantly when shifting from cropland to revegetated grassland.The infiltration coefficient of crusted soil decreased gradually with the increase in years of revegetation.However,the infiltration coefficient increased gradually when getting rid of the crust.4)The formation of the biological crust brought to an enrichment of soil organic matter and total nitrogen in the upper soil.With the increased years of rehabilitation,the enrichment was even more obvious,and soil total phosphorus was also enriched to some extent.Soil available nutrient was improved as a result of the formation of the biological crust.