Soil water is an important factor to the land use and ecological construction on the Loess Plateau.Soil particle size can sig nificantly affect soil moisture.The purpose of this study was to determine the influence of soil particle composition on soil moisture in the sem-iarid area of the Loess Plateau. Caragana landand cropland were selected in Suide County, Shaanxi Province and soil moisture, as well as particle size,from surface to 18 m deep was tested. Results showed that soil moisture was significantly influenced by clay content below 3 m depth on cropland and below water consumption depth of caragana shrub. The relationship between soil moisture and clay content could be best simulated by logarithmic function. Within water consuming depth of caragana shrub, the impact of soil particle composition on soil moisture was not significant.