Abstract: The improved flushing method was used, and Pinus tabulaeformis,Platycladus orientalis and other 6 tree species were selected to measure the water potential and hydraulic architecture parameters of twigs, in order to study the water conditions and seasonal changes of the hydraulic architecture of these 8 greenery tree species.Results showed that the water potential of the 8 tree species exhibited an obvious “single-peak” trend; monthly change range of K_h and K_s which reflected the vulnerability of xylem embolism showed the following order: Sophora japonica,Ligustrum lucidum,Salix matsudana and Cotinus coggria>P. tabulaeformis,P. orientalis and Sabina vulgaris> Buxus microphylla; The change range of LSC accorded to that of K_s, and the LSC of S. japonica and C. coggria had no obvious decline when their leaves fell after October, which indicated that this strategy of plants was likely to be important to the water condition of the reserved leaves. As a CAM plant the water potential of B.microphylla kept a lower level, and its hydraulic architecture parameters were different from other tree species, which might be related to its different photosynthestic paths.