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Cave oxygen isotope (δ18O) records have been important in characterizing Asian Monsoon variations on a wide range of timescales. The climatic significance of the δ18O proxy of the cave records and its main control factors, however, remain hotly debated, especially with respect to annual to decadal timescales. In particular, while the spatial and intensity variations of the Western Pacific Subtropical High (WPSH) affects the East Asian Monsoon remarkably on annual to decadal timescales, cave records up to present do not show clear evidence of the WPSH signal. Here we report a new high-resolution (average of 1.5 months) δ18O record from Dongshiya Cave, Qinling Mountain, central China. The region is highly sensitive to variations in the position of the WPSH western boundary, which in turn regulates the alternation of dominant moisture sources between the proximal Pacific Ocean and the remote Indian Ocean. Together with another cave record near the WPSH western boundary, we established a new index to reconstruct variations of the WPSH western boundary over the past 200 years. Our new data revealed two significant periodicities, 12 and 2-7 years respectively, that can be causally linked to solar and ENSO variances correspondingly. [ABSTRACT FROM AUTHOR]