The research area of this study was the Wangmao ditch small watershed in Suide county of the Loess Plateau of China. Combining with the field investigation and laboratory test, the variations of stable isotopes (δ2H) in the vadose zone under three different land use types were studied in a single rainfall event. The results showed that: (1) The soil water content ranged from 6.74% to 21.42% in grassland, from 6.74% to 19.08% in woodland, and from 7.86% to 20.74% in farmland. The variation ranges of soil water storage were from 265.6 mm to 384.0 mm in grassland, from 275.1 mm to 368.7 mm in woodland, and from 289.5 mm to 334.6 mm in farmland. The variation ranges of δ2H in soil water were from -113.41‰ to -71.84‰ in grassland, from -115.10‰ to -50.98‰ in woodland, and from -112.28‰ to -63.78‰ in farmland. (2) There were two trends in soil water content changes in grassland, woodland and farmland, but with difference in time nodes. (3) There were significant differences in the hydrogen isotopic changes of soil water in different land use types. The farmland and grassland were favorable for the soil water retention, but it was not easy for the woodland to maintain soil moisture. (4) The peak values of soil water storage under different land use types were inversely related to the water storage capacity. The higher the peak value, the lower the corresponding water storage capacity. (5) There were preferential flow phenomena in all land uses studied, with the largest preferential flow in woodland. The path of preferential flow was extended in grassland and woodland , whereas in farmland, it might be affected by the quality and recharge of groundwater .