In order to investigate the relationship between deep soil water (below 2m) vertical variation and root distribution in the nine-year-old dense jujube plantation in Loess hilly region. The soil core method and oven drying method were used to determine fine root dry weight density and soil water content. Sequential cluster analysis method was adopted to stratify the whole soil water profile into three layers, i.e. strong depletion layer (2.0~4.4m), less strong layer (4.4~5.0m) and weak depletion layer (5.0~7.0m) based on the combined analysis of soil water content and the root dry weight density. This stratification result could well reflect soil water characteristic absorbed by root. In the strong depletion layer, fine root dry weight density decreased fluctuantly with the increase of soil depth, but soil water content was low and stable. While in the less strong layer, fine root dry weight density decreased continuously, soil water content presented increasing tendency. The maximum fine root depth was 5m, there was no fine root in the weak depletion layer and soil water content increased obviously. This study determine the soil layer range of deep soil water depletion degree in densely jujube plantation. It shows that root distribution characteristic has an important effect on the deep soil water variation. 