Stomatal conductance (gs) and leaf water potential (ΨL) were measured in situ with LI-1600 porometer and PMS pressure chamber, respectively, to investigate the mechanism involved in the response of stomatal conductance to the changes of environmental water status in leaves of tree species in different successional stages of subtropical forest. Two stronger light-tolerant or early-successional species, Rhodomyrtus tomentosa and Evodia lepta, one mesophytic-biased sun plant, Schima superba, and two shade-tolerant or late-successional species, Schefllera octophylla and Psychotric rubra were selected in this study. The results indicated that the leaf hydraulic conductance (KL), namely the leaf specific hydraulic conductance between soil and crown leaves, reduced with the declination of leaf water potential (ΨL) in all examined species. Corresponding ΨL at the initial minimum values of KL was -1.60, -1.42, -1.30, -0.9 and -1.05 MPa for R. tomentosa, E. lepta, S. superba, S. octophylla and P. rubbra, respectively. In situ gs measurements showed that ΨL at the initial time of stomatal closure, which referred to the ΨL point when gs started to decline, was -1.58, -1.52, -135, -1.02 MPa and -1.0 MPa in the above mentioned species, respectively. The results may allow us to infer a linkage between diurnal changes in KL and gs. The observed trends in gs and KL in response to the change of ΨL across the successional species suggest that the early-successional species, R. tomentosa and E. lepta, were capable of maintaining high stomatal conductance at more negative ΨL under water stress. This hydraulic property may allow these species to photosynthesize and maintain dominantly under higher water stress conditions. However, higher ΨL would trigger stomatal closure and reduction of photosynthesis in the late-successional species, S. octophylla and P. rubra, which may be one of the potential factors affecting the general trend of forest succession in subtropics if environment becomes drier caused by climatic warming.