Variations of bulk leaf water stable isotopes can indicate mass and energy exchange between the inside and outside of the leaves, and can also reflect the climate and ecological conditions of the areas in which plants live. Moreover, leaf water in plants plays a significant role in the hydrological cycle. Understanding the stable isotope composition of leaf water is helpful to reveal the distribution and contribution of leaf water stable isotopes to the local water stable isotope cycle. This paper reviews the advance in the study of stable isotope composition of leaf water in plants. It is clear that stable isotope fractionation of water in plants would not take place until it entered into the leaves, and there are three types of isotope fractionation-equilibrium, kinetic and biochemical isotope fractionations in the leaves. The factors impacting on the stable isotope composition of leaf water include the meteorological conditions such as air temperature, relative humidity, atmospheric pressure, and wind speed as well as the ecological conditions such as transpiration rate, stomatal conductance, and so on. Similar as that of precipitation, the linear relationship also exists between δ¹⁸O and δD of leaf water in plants. However, the slopes of the regressive lines are significantly lower than those of some Local Meteoric Water Lines (LMWLs). Furthermore, some leaf water models, such as the steady-state (modified Craig-Gordon) model, string-of-lakes model, steady-state model including the Péclet effect, non-steady-state model (including the Péclet effect or not), and two-dimensional model are interpreted. In addition, this paper discusses some problems in the study of leaf water stable isotopes, and suggests some possible trends for future research on the relationship between stable isotope composition of leaf water and meteorological and ecological factors, the signals of the deuterium excess of leaf water and of the slope and intercept of evaporation line for leaf water, the validation of the models in China, especially cold-arid regions, and the application of stable isotopes of leaf water in water cycle.