Abstract: The water ecophysiology of eight tree species growing in dry and hot valley of Jinsha River was studied. The result showed that in rain season the index of water saturation deficit (WSD) of indigenous tree species Dodonaea viscosa Jacg, and three eucalyptus species were higher than that of the other tree species. The plant with high WSD index and low relative water content (RWC) has strong drought tolerance. Enlargement of the rate of leaf area and fresh leaf weight is beneficial to enhance the drought tolerance of a plant, while increasing the accumulation of dry materials and the density of cytoplasm is also an effective way. Dry and hot stress may induce chlorophyll content reduced, while the chlorophyll content may increase in rainy seasons with increasing the rate of chlorophyll a and chlorophyll b. In dry seasons, the sugar content of test trees is higher than that in rainy seasons and the starch and sugar contents are lower in dry reasons than in rainy reasons except Acacia manguim De Willd. Under the arid condition, the free proline content of 7 tree species increased with different degrees except Eucalyptus urophylla S. T. Blake. The tree species which are prone to wither and defoliation in dry seasons can accumulate more free proline. There are more ecophysiological similarities among the seven tree species which are suitable for afforestation except Acacia manguim De Willd.; and there exists obvious consistency in ecophysiological characteristics among same genus. Some ecophysiological characteristics of D. viscosa Jacg., the indigenous tree species, are similar to that of Acacia and some others are similar to that of Eucalyptus. Three Eucalyptus species, three Acacia species and D. viscosa Jacg. showed stronger ecological adaptability and grow well in dry and hot valley of Jinsha River.