The vertical variations of different types of soil moisture in Yan'gou watershed in the hilly and gully area of the Loess Plateau are analyzed.Results show that the variation of soil moisture content in different layers is great under the condition of designed experiment.Soil moisture contents on dam

terrace

and slope are consistent with the seasonal change of rainfall.Soil moisture content of 100-200cm layer in orchard fluctuates significantly with the seasonal change of rainfall.The variation of soil moisture content is different in extent not only under the different land types

but also under the same land type.The variation coefficient of soil moisture content is the biggest at 10cm depth and is gradually reduced with increased soil depth.According to the analysis of the variation coefficient

the vertical distribution of soil moisture content under different land types may be divided into vertiginous layer

active layer

subactive layer

and relatively stable layer.Regression equations of the variation coefficient are also found for the soil layers of different land types.