The eolian deposits on the Chinese Loess Plateau (CLP) are key archives of late Cenozoic climate changes and atmospheric circulation, However, the long-standing controversy about the stability of dust sources over the last-6 Myr limits our understanding of the genesis of the CLP and its paleoenvironment implications. Here we report that an abrupt decrease in K isotope compositions (delta 41K) of the CLP eolian deposits occurred at-2.58 Ma, with loess/paleosol displaying delta 41K values (-0.41 %o to-0.63 %o) lower than the bulk-silicate-earth-like Red Clay values (-0.35 %o to-0.45 %o). Furthermore, The delta 41K values of eolian deposits are negatively correlated with the Na2O/K2O and Na2O/Al2O3 ratios, with negligible influence from different grain size fraction. These observations indicate that the delta 41K values are not controlled by post-depositional weathering at the CLP, but rather by an increased export of weathered detritus or recycled sediments from the Northeastern Tibetan Plateau, as revealed by K isotope surveys of potential source materials and Earth system model simulations. Our results further suggest that the intensified global cooling during the Quaternary promoted greater sediments erosion and altered the dynamics of the westerlies and the Siberian High, with important implications for understanding the paleoenvironment changes and reconstruction of the East Asian atmospheric circulation across the Pliocene-Pleistocene boundary.