A study on soil water regime under different plant coverage was carried out in the east of Hunshandake sand land. The results
show that the soil water content in 0-10cm layer of nearly bared mobile aeolian sandy soil fluctuates intensively, and the average soil water content through the whole growth season is very low. That in the soil deeper than 10cm is about 3% through the whole growth season ,and is relatively stable. The soil moisture is for scrub absorbing mainly in the depth from 30 cm to a depth of lower than 110 cm. The soil moisture for herb is mainly in the layer of 20-90 cm. In the
arid and semiarid region, plant decreases the depth of rainfall-moistened layer in soil. The available soil water distributes to shallow layer. And the distribution of rainfall in soil profile and the depth of rainfall-moistened soil confine the plant rhizotaxis, and determine the direction of
vegetation succession and the type of climax community. As a feedback regulator, soil water makes the vegetation in arid and semiarid region become negative feedback system. The high sand dune may be an important environmental resources for plant to escape drought in the arid and semiarid region.