Abstract: This paper described the application of stable hydrogen, carbon and oxygen isotopes techniques in tracing sources of plant water and water use efficiency. Since the process that plant roots uptake water is nonfractionating, plant xylem water has the same composition of stable hydrogen and oxygen isotopes as soil water utilized by the plant. By analyzing the composition of hydrogen and oxygen isotopes of plant xylem water and potential sources of water, we could quantitatively determine the contributions of the sources to plants. For the study of water use efficiency, there were many researches showed that the composition of stable carbon isotopes of leaves can be an indirect indicator of plant water use efficiency. Photosynthesis is one of the most significant processes of carbon isotope fractionation in nature. So, stable carbon isotopes techniques had become the best way to study the longterm water use efficiency of plant leaves presently. As a safe tracer material, stable isotopes technique will help people to understand the plant’s ecophysiological process. Anyway, with the continuous improvement of techniques, stable isotope techniques will be widely used in many areas of ecology.