According to the observed data from loess hilly region at Ansai county in 1998

soil moisture of 5～7 year seabuckthorn stands and its influence on seabuckthorn growth are studied．The experimental results showed that：(1) The absorption range of seabuckthorn roots can extend a depth of under 2 m layer

at the scope of 2 m layer

the characteristic of vertical variation of soil moisture of woodlands is that

soil moisture has a tendency of decreasing with the depth of layer increasing

there are two strong absorption layers of soil moisture at 30～50 cm and 80～100 cm layer; (2) The seasonal variation of soil moisture under seabuckthorn woodlands may be divided into three periods： deficient period

accumulative period and lessen period．In 1998

annual precipitation is much even

soil moisture has two obvious seasons of dry and humid; (3) In the annual growth season

the growth of seabuckthorn has marked correlation with soil moisture of woodlands

and seasonal variation of growth falls behind that of soil moisture．