The water parameters and their seasonal changes of Malus micromalus,Prunusameniaca var ansu and Elacagnus angustifolia are studied by using P-V technique under field condition. The adaptive responses of the tested trees are explored under drought stress condition. The results show that the regular patterns of the seasonal change of water parameters for thesespecies are related to climate conditions,especially the water element,and the phenologilcal char-acteristics formed by adapting to the climate condition over a long period.Within growing sea-son,the weakest point of drought tolerance of these species is in spring and early summer whenyoung branches and leaves are growing,The drought tolerance becomes stronger with droughthardening and branches maturating. The idex of drought tolerance fluctuates during the growingseason. The value of and drotight tolerance index can be used as an indicator for judging thedrought tolerance of the three species.