In order to study the effects of Robinia pseudoacacia forestlands with different densities on soil moisture in the loess region of Western Shanxi Province, the R. pseudoacacia forestlands with densities of 2 400 per hacter and 1 300 per hacter were selected to represent the high and low density R. pseudoacacia forestlands in the study area respectively, and the bare land as a control. The soil water content in 0-150 cm range and precipitation outside the forest were carried out by using Enviro-SMART soil moisture positioning monitoring system and self-recording dump rain gauge. The results showed that:(1) In different precipitation years, the average soil water storage of low-density R. pseudoacacia forestland was higher than that of high-density R. pseudoacacia forestland in drought and normal years. In these years, the absolute value of annual average soil water storage of low-density R. pseudoacacia forestland was 6.80 mm higher than that of high-density R. pseudoacacia forestland. (2) In the vertical direction of soil profile, the water consumption of 0-30 cm soil layer by high-density R. pseudoacacia forestland was higher than that of low-density R. pseudoacacia forestland in drought and normal years, and there was no significant difference in soil moisture consumption between these two kinds of R. pseudoacacia forestlands in wet years(P>0.05). (3) Comprehensive analysis of rainfall infiltration depth, infiltration amount and compensation degree of soil moisture in rainy season, natural rainfall in the study area could effectively supplement the soil moisture consumed by low-density R. pseudoacacia stand growth, and there was no new ecological degradation caused by water shortage in the process of vegetation restoration in the Loess Plateau. However, considering the consumption of soil moisture by high density R. pseudoacacia forestland, it was suggested that low density R. pseudoacacia forestland should be popularized in vegetation construction in the study area.