Water contents of sandy soil and loess in Jingbian County, Shaanxi Province are studied through the field investigations and measurements. Experimental results show that water content of sandy soil is less than 3% and water content of loess under poplar trees, about 7%. Severe dried layer occurs in sandy soil and moderate dried layer under poplar trees, in loess. All the dried layers are above 6m in depth. The degree and depth of dried layer indicate that natural arid climate is a dominant factor causing dried layers in the area, with the tree species being an important factor. During ecological and environmental construction, different types of vegetation should be recovered in view of the different levels of dried layer development. Grass and bush should be planted in the sandy soil area and grass and drought tolerant bush with trees should be plan-ted in the loess soil area. Where dried layers develop severely, afforestation is unsuitable because it can not bring environmental and economical benefits, but can cause excessive consumption of deep soil moisture and underground water.