SBased on the soil desiccation and water shortageSproblems inSthe semi-arid Loess Plateau in China, the soil water and temperature ofS0-1000Scm soil layers in a dense jujube plantation was measured duringS2012 to 2015 in order to investigate the mechanism of soil water loss in jujube plantations in the region.SThe results of our analysis showed thatSevaporation is the main reason of the soil water loss in non-growth period: the soil water moved toward the upper soil layer and eventually converted to water vapor when near the soil surface, then diffused into the atmosphere. The soil water loss in the non-growth period is serious: the amount of soil water loss in 0-200 cm soil layerSwasSup to 85.64-92.34 mm, which is about twice as much as contemporaneous rainfall. BothSthe water loss amount and the net flux of soil water vapordecreased with the increase of soil depths in the 0-540 cm soil profile. The most active layer of soil water loss is 0-11 cm.