The analysis of stable isotope composition is an important tool in research on plant physiological ecology. However, large-scale patterns of leaf stable isotopes for aquatic macrophytes have received considerably less attention. In this study, we examined the spatial pattern of the leaf δ13C and δ15N of macrophytes collected across the arid zone of northwestern China and tried to illustrate how they were affected by different environmental factors. Our results showed that the mean values of leaf δ13C and δ15N in the macrophytes sampled from the arid zone were -24.49‰ and 6.82‰, respectively, which were drastically higher than the values of terrestrial plants. In addition, leaf δ13C varied significantly among different life forms, possibly reflecting the complex photosynthetic fixation and adaptations of macrophytes. In addition to, our studies indicated that the foliar δ13C values of all the aquatic macrophytes were only negatively associated with precipitation, but the foliar δ15N values were mainly associated with temperature, precipitation and potential evapotranspiration. Therefore, we speculated that the determinant of the leaf δ13C of macrophytes in the arid zone of northwestern China is water factors and the leaf δ15N values is the complex combination of water and energy factors.