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As an important component of the "Asian Water Tower", lakes on the Tibetan Plateau (TP) significantly affect the regional ecosystems and societies, and they serve as an effective sentinel of climate change. Therefore, a good understanding of the long-term hydrological variations of these lakes is necessary. However, the Holocene lake-level fluctuation on the northwestern TP (NWTP), an important region for the interaction between the Indian summer monsoon (ISM) and the westerlies, remains unclear largely due to the challenge in dating of lake (shore) sediments [1]. Here we present the lake level variations of a non-glacier-fed lake, Longjue Co, on the NWTP based on luminescence dating of the paleo-shorelines. The OSL signals of quartz grains are unsuitable for dating due to high contributions of the medium component. The post-infrared infrared stimulated luminescence (pIR50IR170) signals of K-feldspar single-aliquots are favorable as indicated by internal checks including dose recovery tests, residual dose tests and measurements of signal stability. However, incomplete bleaching of the signal for part of the samples were found by comparing the IR De/pIRIR De ratios of all the samples [2]. Thus, the pIRIR dating of K-feldspar single-grains (SG) were further performed on the poorly-bleached samples. After rejecting grains with unfavorable signals, the dependence of the De of Kfeldspar grains on their brightness were examined and the brightest grains were used for De calculations. The Minimum Age Model and the Central Age Model were used for poorly-bleached and well-bleached samples, respectively. The results show that Longjue Co reached the highest level during the early Holocene (10-8 ka) and then gradually shrank in the middle and late Holocene. The correlation with paleo-climate records suggests that the Holocene shrinkage of Longjue Co is mainly modulated by the gradual weakening of the ISM, which follows the trend of Northern Hemisphere summer insolation. Our results indicate that the NWTP was significantly influenced by the ISM during the Holocene. In addition, we highlight the necessity of SG luminescence dating for water-lain sediments dating on the TP. [ABSTRACT FROM AUTHOR]