Abstract: Abstract: Jujube is a kind of perennial fruit tree in arid and semi-arid areas in central and eastern Asia. Since the initiation of the large-scale ecological rehabilitation project (known as "Grain for Green" project) by the Chinese central government in 1999, the area of jujube orchards has been increased rapidly in the loess hilly region mainly for conserving soil and water and raising economic benefits. Here we investigated the variation of root-zone soil water with a range of stand ages (2, 6, 10 and 15 years) in a rain-fed jujube (Ziziphus Jujube Mill. cv. Lizao) plantation in Qingjian County, Shaanxi Province (37°15′N, 118°18′E). A portable time domain reflectometry (TDR) system (IMKO, Ettlingen, Germany) was used to monitor the soil profile water in study sites. Sixteen tubes with the length of 3 m were installed at a distance of 0.3 m from the representative tree trunk for each stand in October, 2013. Soil water content was measured once every 2 weeks from May to October in 2014 and 2015. The results showed that: 1) During the growth period of 2014, soil water content in the 2- and 6-year-old jujube trees increased first with depth and peaked in the 0.6 m soil layer, and then decreased gradually with depth, while the peak position of soil water content in 10- and 15-year-old jujube trees were both in the 0.4 m soil layer. However, the peak position of soil water content in 2015 was 0.2 m deeper than that in 2014 in all study sites due to serious drought. There were different monthly dynamics of soil water content in study sites during the growth period between 2014 and 2015. In 2014, soil water content was the lowest in June (from May to October), which was increased greatly in August and reached the maximum value in October, whereas there was declining tendency of soil water content from May to September in 2015. 2) The precipitation was relatively abundant in the period from July to September in the study area, which accounted for 70% of the rainfall during the jujube growth period. Soil water contents of 0-0.6 m layers in all study sites were greatly affected by precipitation and evapotranspiration, which increased clearly following apparent rainfall events; the mean soil water content in 2-year-old jujube tree was consistently greater than that in other stand ages in the 0.6-1.8 m soil layers, and there were significant differences in soil water contents among different stand ages (P<0.05), which meant that the soil water content had been utilized by roots in the 0.6-1.8 m soil layers, and the water depleted increased gradually with stand age. Soil water contents in the deep soil layers (1.8-3.0 m) were weakly affected by precipitation, which showed almost constant values at all study sites, and soil water contents in the deep soil layers were approximate to permanent wilting point (7%) in the mature jujube plantation (10-, and 15-year-old jujube trees). 3) It could be observed that in June 2014, before the typical rainfall, the mean soil water contents in the 2-, 6-, 10-, and 15-year-old jujube trees were 15.76%, 13.38%, 12.93%, and 12.36%, respectively, which were all in low humidity (less than 60% of field capacity). However, soil water contents increased dramatically in the 0-0.8 m soil layers in 2- and 6-year-old jujube trees following 90.4 mm precipitation (June 8 and June 11 in 2014), while the soil water contents were significantly increased only in the 0-0.6 m soil layers in 10- and 15-year-old jujube trees under the same conditions. Soil water changed negligibly beneath 1 m after the rainfall, indicating unavailable infiltration in deep soil. The results presented here will be helpful to water management in rain-fed jujube plantations in the loess hilly region and maybe potentially for other semi-arid orchards.