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．