Aeolian systems, including deserts/dunefields and downwind loess regions across the mid-latitudes of the Northern Hemisphere, are important components of global terrestrial ecosystems. These aeolian systems respond sensitively to large-scale atmospheric circulation patterns via aeolian activity and dust emissions. However, it remains unclear whether earth surface processes and their dynamics were identical across these regions in northwestern China during the late Quaternary. Using end-member analysis (EMA) of a typical loess-aeolian sand sequence, this study reconstructs a detailed history of aeolian activity from the western part of the desert-loess transitional belt since 20 ka. The results indicate that grain size component EM2 (peak at-126 mu m) is a dependable proxy of regional aeolian activity, as it is primarily transported via saltation from proximal sources. Aeolian intensity gradually decreased after the Last Glacial Maximum, reached a minimum during 9.0-5.0 ka, and then intensified. This pattern is consistent with regional syntheses of aeolian archives from comparable settings. However, it differs substantially from the aeolian history of the upwind Tengger Desert hinterland, which recorded the weakest aeolian activity during-7.0-3.5 cal ka BP. This suggests the spatio-temporal heterogeneity of the environmental evolution of the aeolian-loess sedimentary system of northwestern China. Quantitative analyses indicate that aeolian processes across the northwestern margin of the loess-desert transitional belt were primarily modulated by the Indian Summer Monsoon throughout both the past 20 ka and the Holocene. This assessment distinguishes the region from the upwind desert areas, where the evolution of various atmospheric circulations and their interactions played a more important role. Our findings provide spatiotemporal evidence of the divergent environmental evolution between the desert-loess transitional belt and the upwind desert region in northwestern China. Especially, they highlight different trajectories of aeolian activity under global warming, indicating the need for region-specific strategies to combat future aeolian desertification.