A field investigation in the flat sands of southern Maowusu sandy land showed that artificially cultivated single line Salix psammophila could accumulate sand because the plant decreased the windward and leeward wind velocity. There was a significant correlation (R = 0. 696) between accumulated sand volume (V2) and plant volume (V1). When the wind velocity at 4 m height of single-line S. psammophila was 6 m x s(-1), the wind velocity decreased at 3H windward, increased at 2H windward, and then steeply decreased leeward, reached the lowest value at 1H leeward and gradually recovered to the open field velocity. The protection distance of single-line S. psammophila was about 17 H', and the effective protection distance was about 13 H'. Single-line S. psamnmophila had little effect on the wind velocity above plant height.