To understand status and roles of shrub in vegetation degradation and recovery processes in semiarid areas,China,we investigated effects of shrub canopy on soil properties,organic litter,seed bank and understory herbage community properties in Horqin sand land,Mongolia. The results showed that in shifting sand dunes,very find sand,silt,clay,organic matter,total N and P,available P and soil moisture in 0—20 cm depth were 17.3%,4.4%,49.5%,43.8%,40.0%,23.1%,16.3% and 10.8% higher for Caragana microphylla,and 3.5%,21.3%,0.0%,20.0%,16.7%,8.3%,10.6% and 28.1% higher for Salix gordejevii,respectively under canopy of remnant shrub species than those in open space; average organic litter output was 18.3 times for C. microphylla,365.2 times for Artemisia halodendron and 15.5 times for S. gordejevii, respectively,under shrub canopy compared to open space; soil seed density was 10.9 times higher under A. halodendron canopy than that in open space; perennial herbage Pennisetum centrasiaticum belonged originally to fixed sand dune not only could survived under shrub canopy in shift sand dunes,but also had higher plant densities,height,coverage and above ground biomass. There were a significant gradient of organic litter mass,soil seed bank density and plant density under shrub canopy,decreasing gradually from the centre of shrub canopy to the edge of the canopy,and disappeared entirely in open space of one to two meter distant from the shrub canopy. These results suggested that shrub had significant “fertile island” effects and important “keep species” roles in shifting sand dunes.