Soil moisture is an important refereed index for controlling desertification, breeding sand fixing plants, restoring and reconstructing degraded ecosystem. Soil moisture dynamics(0-80 cm) under different underlying surfaces(7-year-old Pinus elliotii, 4-year-old Pinus elliotii, grassland and bare sandy land) in the sandy land of the Poyang Lake were measured and analyzed. Results are as follows: (1) The underlying surfaces, in order of decreasing average soil moisture content, were 4-year-old Pinus elliotii(5.22%), grassland(4.88%), 7-year-old Pinus elliotii(4.01%) and bare sandy land(2.95%). (2) All of the annual soil moisture contents at different depths under different underlying surfaces showed moderate variation. The variation coefficient under the 4-year-old Pinus ellioti was the highest, while that under the bare sandy land was the lowest. (3) There were seasonal changes in the vertical variation coefficients of soil moisture content under different underlying surfaces. The variation coefficients in August were the highest, followed by those from October to December. The smallest variation coefficients were observed from Match to June. Apart from August and October, the vertical variation coefficients for the underlying surfaces with vegetation coverage were lower than those of the bare sandy land.