Abstract: A corridor exists for the transport of aeolian sediments from Badain Jaran Desert to Ulan Buh Desert, but little attention has been paid to the physicochemical properties of the sediments in previous studies. Surface samples were collected in this work from crests of sand dunes along the sand transport belt, with sampling alignment following both prevailing wind direction and orientation of the sand transport belt, grain size composition and constant element contents of the samples were then measured and analyzed. The surface sediments are found to be mainly composed of medium sand, followed by fine sand, with an average particle size of 1.66 Φ. The sediments exhibit good sorting, with a positively skewed and moderately peaked distribution. The constant elements in the surface sediments are primarily SiO₂ and Al₂O₃. Compared to the upper continental crust, except for SiO₂ and MnO showing enrichment, all other elements are deficient. The mineral maturity of surface sediments in sand dunes is higher than the BadainJaran Desert. Medium sand, fine sand, and coarse sand in the surface sediments of sand dunes in BJD-UBD contribute significantly to the enrichment of SiO₂, K₂O, and MnO. Spatial consistency is observed in variations of grain size and major element enrichment/deficiency. Along the prevailing wind direction, surface sediments in the sand transport belt exhibit a clear trend of fining. Concurrently, SiO₂ content shows a significant decreasing trend, while Al₂O₃, CaO, K₂O, and Na₂O contents increase significantly. In contrast, mineral maturity displays a non-significant decreasing trend. The surface sediments of sand dunes in the sand transport belt are coarser than the upwind Badain Jaran Desert, indicating that local sediment sources such as regional river channels or alluvial deposits from foothill floodplains may have contributed to the sedimentation of the sand transport belt during its migration from the Badain Jaran Desert. These data provide some scientific basis for the study of formation and evolution of deserts, and the process of wind and sand landforms in the Alxa Plateau.