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The content and hydrogen isotope ratios of n-alkanes extracted from recent lake surface sediments sampled from nine lakes in three different climate zones on the Southwestern Tibetan Plateau were analyzed. Values were compared with n-alkanes in plants from lake drainages, and δD values of meteoric water, lake water, and mean annual precipitation. The results showed that n-C was predominantly derived from aquatic plants, and n-C- n-C from terrestrial higher plants. The average carbon chain length of n-C- n-C (ACL) was positively correlated with the mean annual precipitation. δD values of the long-chain n-alkanes n-C and n-C of terrestrial origin (varying between −214 ‰ and −169 ‰, and −226 ‰ and −185 ‰, respectively) were inversely correlated with mean annual precipitation; but in accordance with the average annual variations in δD (OIPC), δD values of n-C were strongly related to the δD values of growing season meteoric water ( R = 0.74). The large difference between δD values of n-C of aquatic origin and n-C (an average of about 27 ‰) demonstrates the enrichment of the lake water δD compared to precipitation, caused by strong evaporation in the semiarid-arid areas of the southwestern Tibetan Plateau. Average value of $$ \varepsilon_{n\text{-C}_{25-31}/\text{p}} $$ (−95 ‰) is evidently higher than the value observed in European wet regions (−128 ‰); besides, $$ \varepsilon_{n\text{-C}_{31}} $$ (about −116 ‰) is constant along the study transect (SD = 9), which indicates that n-C is a useful proxy for the environment. [ABSTRACT FROM AUTHOR]