Soil moisture levels in cultivated grasslands were studied in a dry area in China over five years. Leguminous plants like Medicago sativa used more water from deep soil layers and grew more biomass than gramineous plants like Agropyron cristatum, which mainly used shallow soil water. After five years, A. cristatum had the highest soil moisture content in the 20-80 cm soil layer. Leguminous grasslands caused a serious water shortage in deep soil layers. Planting A. cristatum may be a good choice for restoring grasslands in dry areas to sustain water resources.