Large-scale vegetation restoration in the Loess Plateau has had a major impact on the soil moisture content and soil organic carbon (SOC), as well as soil water conservation and carbon sequestration services in this region. The response of deep soil moisture and SOC contents to vegetation restoration raised serious concerns in current studies regarding eco-hydrology and ecosystem services in the Loess Plateau. However, limited studies have examined the responses of deep SOC and soil moisture along with their coupling relationships to vegetation restoration in this critical area. In this study, vertical distribution (0-5 m depth) of SOC and soil moisture contents in different human-introduced vegetation types (grassland, shrubland and forestland) and restoration ages in a typical loess hilly watershed were analyzed, and soil moisture and SOC contents in cropland were measured as controls. Our analyses showed that:(1) Soil moisture deficit was observed in different human-introduced vegetation types. The surface soil layer (0-1 m depth) had the lowest soil moisture deficit, and the 2-3 m depth layer had the highest soil moisture deficit. In forestland, soil moisture deficit was significantly greater in the 21-30a stage than that in the previous stage (11-20a), and subsequently decreased after 31 years of growth. However, soil moisture deficit in shrubland and grassland increased subsequent to abandonment of croplands. (2) The mean SOC contents of forestland, shrubland and grassland in the 0-5 m depth profile were 1.97, 1.77, and 1.72 g/kg, respectively. Soil carbon sequestration in forestland increased with increasing restoration ages, and exhibited net gain in the 20a stage compared with cropland. Carbon sequestration in shrubland increased initially, but then decreased with increasing restoration age. In contrast to forestland and shrubland, carbon sequestration in grassland decreased with increasing restoration age, and was lower than that of control farmland for all restoration stages. (3) Soil moisture content in the surface layer (0-1 m depth) did not exhibit significant changes with increasing restoration age. However, soil moisture content significantly decreased in deep soil layers with increasing restoration age. Nevertheless, no significant correlation was found between levels of SOC and restoration age at any soil layers tested. In deep soil profiles, soil moisture content and SOC exhibited significantly positive correlations. Furthermore, the rate of increase of SOC was lower than that of soil moisture content. These findings indicated that deep soil carbon sequestration was closely related to soil moisture content. The soil carbon sequestration process may require adequate soil moisture at greater soil depth. Deep soil moisture deficit may restrict carbon sequestration in deep soil layers by constraining fine root development.