By taking the typical walnut-peanut intercropping system in the loess region of West Shanxi Province as the study object, the effects of soil moisture in different layers of soil profile (0-100cm) were studied using the traditional weighing method in 2008. Results showed that (1) the seasonal variation of soil moisture was very significant in the intercropping system. (2) Soil moist ure content increased with the increased depth of soil in vertical direction and the variance of soil moisture in 0-40 cm soil layer was strong. Soil moisture content increased with the increase of the distance from treerow and then became stable in horizontal direction. The curve of soil moisture could be described by a parabola equation. (3) Soil moisture had positive effects in the intercropping system, comparing to peanutsole cropping. The analysis indicated that there was an ecological niche overlapping between trees and peanut, which may negatively impact the production of peanut , but the competition between fruit trees and crops was not strong.