Soil moisture content of Robinia pseudoacacia plantation was monitored at fixed points to investigate the distribution and deficit degree of soil moisture of R. pseudoacacia plantation at different ages. Using the method of spatial sequence instead of time successional sequence, 10, 15, 25 and 40 years R. pseudoacacia plantations were selected as the research objects, and farmland (0 years) was served as control to investigate and analyze the distribution of soil moisture content in the 0-200 cm soil layer. The results showed that the average soil moisture content was in order of 0 years (18.80%)＞10 years (16.43%)＞15 years (15.47%)＞40 years (13.87%)＞25 years (13.38%). The soil moisture deficit was found in all stands and showed an increase trend with the increasing of stand age. The average degree of soil moisture deficit was 19.38%, the highest value was observed in the 25 years plantation (27.76%), and there was a slight recovery in the 40 years plantation (25.80%). The variation degree of surface soil water was the largest, and it increased with the increasing of stand age. The four levels of rapid change layer, active layer, sub-active layer and relatively stable layer were only observed in the 40 years plantation. The above research results could provide a certain theoretical basis for vegetation ecological restoration and scientific management of plantations on the Loess Plateau.