Qinghai Lake is China’s largest inland saltwater lake. The n-alkanes and their hydrogen isotopes in aquatic plants from Qinghai Lake and terrestrial plants from the surrounding area were analyzed using GCMS and GC-TC-IRMS. The result shows that n-alkanes in different samples range from C15 to C33 with a single peak distribution. The main peak carbon is mainly C23 and C25 for aquatic plants, C27 for terrestrial wood plants and C27 and C29 for terrestrial herbaceous plants, showing that the main peak carbon number gradually decreases from terrestrial herbaceous plants, with the exception of T. maritimum, terrestrial woody plants to aquatic plants. CPI and ACL values range from 4.0 to 29.7 and 26.0 to 29.6, respectively, with the latter closely related to the plant species. The δD values of n-alkanes from aquatic plants and terrestrial plants range from -209.8‰ to -85.6‰ (ave. δD value of -169.2‰ to -121.2‰) and -196.7‰ to -84.3‰ (ave. δD values of -173.0‰ to -108.6‰), respectively. There are some significant differences in hydrogen isotopic compositions of n-alkanes between different aquatic organisms and different terrestrial organisms in Qinghai Lake. The results show that the salt content of lakes has a significant effect on the hydrogen isotopes of n-alkanes in aquatic plants and the environmental humidity and precipitation significantly affect the hydrogen isotopic compositions of n-alkanes in terrestrial plants. The average hydrogen isotopic compositions of n-alkanes in the plants decrease with increasing ACL value. Different kinds of plants have different hydrogen isotopic fractionation effects during their synthesis. Compared with terrestrial plants, n-alkanes in aquatic plants are more enriched in H relative to environmental water, and with increasing ACL value, hydrogen isotope fractionation between the environmental water and nalkanes increases.