The concave surfacecharacteristics of sandbag sand barrier of different sizes in different positions of sand dune were studied in this paper. The experimental area is near Jilantai town in the southwest of Ulan Buh Desert.The sand barrier was set in April,2007 and the investigation of the concave surface was finished in April,2008. Results show that the sand barrier size and the setting position have strong influences on the concave surface characteristics.Compared with the 3 sizes,the sandbag sand barrier of 1 m × 1 m size is berreficial to the stable concave surface formulation. Compared with the 3 positions of the sand dune, concave surface on the top of dune is more stable. All the profile curves of N-S and W-E directions in different types conform to the one variable quadratic function, basically. The N-S profile is steeper than the W-E profile. It means that wind strength and wind direction can strongly influence the concave surface characteristics. The erosiorrdeposition coefficient of sandbag sand barrier stable concave surface is about 1/10. The plant in the sand barrier alsocan influence the concave surface characteristics.