Abstract <p>The Qaidam Desert is an important window for the study of extreme arid highland desert. However, quantitative studies on the surface and subsurface grain size characteristics of the aeolian sediments are still weak, especially the systematic exploration of the connection between surface and subsurface sediments is lacking. In addition, the correlation between grain size distribution and mineral content in aeolian sediments has not been reported. This study focuses on the relatively weakly studied western dune region of the Qaidam Basin and reveals the petrological characteristics of the aeolian sediments in this region by analyzing the grain size and mineral content of subsurface and surface samples in detail. The results show that both subsurface and surface samples from the study area consist of four end members (EMs): EM1 (mean 6.84 μm), EM2 (mean 25.80 μm), EM3 (mean 149.30 μm), and EM4 (mean 348.75 μm). The grain size distribution on the dune surface showed an increasing and later decreasing trend of grain size from the bottom to the top, which was mainly controlled by the proportion of EM4 and its grain size variation. The absence of EM3 in the interdune samples may be related to the effect of ‘spiral airflow’. Mineralogical comparisons show that the western Qaidam Desert is the closest to the Taklamakan Desert. In addition, quartz and feldspar contents in the subsurface samples show a significant correlation with EM2, while no similar correlation is observed in the surface samples, which may be related to the differences in preservation mechanisms of aeolian sediments. This study provides a new perspective for understanding the formation and evolution of the Qaidam desert, and supplements the relevant basic data.</p>