Identifying the provenance of aeolian sand is crucial to unraveling the formation and evolution processes of dunes commonly occurring in arid and semi-arid regions. This study presents comprehensive grain size and geochemical data for the mobile dunes (n = 22), vegetated dunes, i.e., dunes stabilized or semi-stabilized by vegetation (n = 26), and fluvial sand samples (n = 10) in the Wulanbuhe (a.k.a. Ulan Buh) Desert (WD) of northwestern China. Major-elemental data and the Al2O3 - CaO*+Na2O+K2O - SiO2 (A-CNK-Si) diagram indicates that dune sands have undergone sedimentary sorting during aeolian transport, although chemical weathering was weak. Spatial variations in grain size and geochemical characteristics within the WD dune sands are not systematically observed, indicating a heterogeneous mixture of materials from diverse sources. Based on the end-members mixing model, this study found differences in the sand sources between the mobile and vegetated dunes in the WD. The bedrock detritus from the surrounding mountains is a dominant source (60 %) of the mobile dune sands in the WD, followed by the paleo-lacustrine deposits from the desert hinterlands (24 %) and the sediments of alluvial fans from the upwind areas (16 %). In contrast, the sands of vegetated dunes were derived from the bedrock detritus (48 %), alluvial fans from the upwind side (32 %), and paleo-lacustrine deposit (20 %), respectively. Our findings confirm that the presence of vegetation on the dune surface influences sediment grain-size characteristics, which in turn affects aeolian erosion and deposition processes, leading to variations in sand source materials.