Plant-water relation is an important part of eco-hydrological process. Its study scope has been greatly expanded with the improved research precision based on the application of stable isotope technique. However, water extraction of plant samples is timeconsuming and laborious, which limits the application of this technology. In this study, we used the vacuum distillation method to extract plant stem water from the same quality of samples of different plant species under the same time gradient. The shortest water extraction time was obtained based on the changing characteristics of water extraction rates and stable isotope values of the extracted water. We further tried to establish the correlation between the shortest extraction time and the wood density. The results showed that the wood densities of three target plants, Rhus chinensis, Alchornea trewioides and Pyracantha fortuneana, were 0.35, 0.55 and 0.67 g·cm^-3, respectively. In addition, the water extraction rates for these three kinds of plant samples with an equal mass (about- 3 g) were roughly close to 100% within 45 min. While based on the isotope analysis of the extracted water, the shortest extraction time for R. chinensis, A. trewioides and P. fortuneana was no less than 45, 60 and 60 min, respectively. The shortest extraction time had a trend to increase with the increase in wood density. These results indicated the probability to establish the relationship between the wood density and the plant stem water shortest extraction time, which would effectively improve the extraction efficiency.