We performed a global scale analysis of available leaf wax n-alkane δD data compiled from our new results, as well as from the literature and expressed as average values of D/H ratios from three common lipids of n-alkanes with odd carbon numbers (n-C27, n-C29, and n-C31) from living higher plants. Our results clearly indicate multiple controls of hydrogen isotope composition and its variability in plants leaf wax. (1) At the global scale, precipitation δD values play a dominating factor that exercises the first order of control for hydrogen isotopic compositions in plant leaf wax. The hydrogen isotopic composition of plant leaf wax tracks the decreasing trend of precipitation δD with increasing latitude. (2) Because of different water acquisition systems, plant life form influences the hydrogen isotopic composition of leaf wax n-alkanes with woody plants and grasses having different responses to the change of global precipitation δD. (3) Physiological difference, due to different photosynthesis pathways or different water usage strategies, can leave an imprint on δD patterns of plant leaf waxes, causing δD variations among plants using the same source water. While these results better explain the variability of hydrogen isotope composition in leaf wax, they also have important implications for the interpretation of n-alkane δD data from fossils and ancient sediments.