Leaf-wax n-alkane hydrogen isotope composition (delta D-alk) is widely applied as a proxy for paleohydroclimatic changes, but the factors controlling delta D-alk remain to be clarified. In this study, in order to determine the dominant controls, we measured delta D-alk in 54 surface soils along a southeast-northwest transect across a steep climatic gradient in China. delta D-alk is positively correlated with annual precipitation delta D (delta D-pann) and better correlated with growing season (April-October) precipitation delta D (delta D-pgs). However, the variability of delta D-pann (38 parts per thousand) and delta D-pgs (35 parts per thousand) does not explain all of the variance in delta D-alk (84 parts per thousand). The apparent fractionation of hydrogen isotopes between n-alkanes and precipitation (epsilon(alk/p)) is significantly correlated with variables related to aridity: relative humidity, rainfall amount, and aridity index (defined as the ratio of average precipitation to average potential evapotranspiration). This result demonstrates the important control of aridity on delta D-alk, which may result from the increasing soil evaporation and plant transpiration, as well as decreasing biosynthetic fractionation, in arid climates. We compiled published delta D-alk data from surface lake/soil sediments in China, and found that aridity effects are pronounced in regions with mean annual precipitation (MAP) < 800 mm. Therefore, we suggest that soil delta D-alk reflects precipitation delta D modified by aridity, with a greater degree of modification in arid environments (e.g., MAP < 800 mm). Future work to quantitatively determine the effects of aridity on delta D-alk is needed to improve the reliability of the application of delta D-alk in paleoenvironmental studies. (C) 2019 Elsevier Ltd. All rights reserved.