The systematical study on soil moisture of natural vegetation in Yan'an experimental area have major significant to recognized environment of vegetation reconstruction, the study results showed as follows. Soil moisture condition of Loess Plateau could ensure the positive succession of vegetation although there is a layer of lower soil moisture in natural vegetation that is a normal natural phenomenon. Furthermore, the layer of lower soil moisture has not fundamentally effect on the natural renewal, succession and forming a stable community of vegetation. The ranges of soil moisture of main plant community types in Yan'an experimental area are listed in the paper.