Abstract: According to measured data from ten meters below surface in the fields of crop land， woodland，grassland，shrub land and orchard with high production，the used soil dry layer with different degrees was found．The hydrological effect of dry layer shows that the model of water cycle has been strengthened in the pathway of soil，vegetation and atmosphere．The transformation from surface runoff to ground runoff may be prevented in vegetation land with high prod uction and outflow in quantity from these lands may also be decreased owing to the great amount of water deficit in soils．It is also pointed out that the ecological effect of dry layer is to weaken the soil water environment of vegetation growth and decrease the regulation of soil water to plant in semiarid area of the loess region．