Trees, especially big ones, have huge and complicated vascular systems which make the long-distance water transport difficult to study. We used the heat dissipation method and deuterated water as tracers to characterize water transport and storage properties of Quercus variabilis trees under the different water stress treatment. The transit time for D₂O transport from the trunk base to the upper branches and the tracer residence time were determined by measuring hydrogen isotope ratios in water extracted from branches sampled in regular intervals. The result indicated that the maxima δD of full irrigation (FI), mild water stress (LWS) and severe water stress (SWS) respectively increased to 586.67‰、997.33‰ and 1364.89‰ after injecting deuterium tracer. There were significant differences in maxima δD among the three treatments. The tracer velocities with LWS and SWS were significantly lower than FI treatment but the tracer half-life and residence time were longer than FI treatment. The branch PLC, sapflow rate, water potential and transpiration rate were also observed. The branch PLC treated with LWS and SWS was significantly higher than FI treatment and the sapflow rate, water potential and transpiration rate were lower. There significantly positive correlations between tracer velocity and leaf transpiration rate (P<0.01,n=27), and between tracer velocity and sapflow rate (P<0.01,n=9). The results indicated that water transport was determined by transpiration rate. The PLC and branch water potential were inversely correlated with tracer velocity (P<0.01,n=27), suggesting that drought stress-induced embolism and lower water potential should increase resistance to water transport. Tracer half-life and residence time increased as water stress increased. Tracer half-life and residence time were significant exponential functions with the branch PLC(P<0.01,n=27), but power functions with the leaf transpiration rate. The times needed for transporting the same volume tracer were increased, indicating that water transport efficiencies were reduced because of PLC, transpiration and storage water variations under water-stress condition. Analyses of sapflow showed that the calculative fluxes of drought treatments within tracer half-life and residence time were significantly higher than FI treatment. The amounts of water carrying the same volume tracer were increased as stress degree increased. The results indicated that the increased water was possibly stored in the sapwood and re- exchanged to transpiration stream when transpiration was strong in the daytime. Quercus variabilis trees should reduce the water transport velocity and efficiency to adapt water stress environment by xylem embolism and storage-water exchange.