Eucalyptus (E.camaldulensis Dehnh) is one of the major plant species in Iran covering vast areas of plantations. This is a fast-growing species with high tolerance to harsh environmental conditions. Nevertheless the water deficiency in soil can be effective on the quality and quantity of plant growth. To study the effect of soil drought stress on water relationship in Eucalyptus (E.camaldulensis Dehnh), an experiment was carried out using weight and drainage Lysimeters in natural condition. The trials were implemented in Shahid Sadoghi control desert research station inYazd for three years. The experiment was done with three treatments, 100% (control), 70% (medium stress) and 40% (high stress) field capacity (FC) in three replicates as complete randomize design. The results showed that the plant physiological behaviors including water potential, relative water content (RWC) and soluble sugar in leaves were affected by water availability for plant. Increasing the amount of soil moisture was not significantly effective on soluble sugar levels in roots and leaves proline levels (P-value> 0.05). By increasing the amount of soil moisture, the relative water content (P-value <0.001) increased. Increasing the amount of soil moisture reduced the water potential (P-value <0.001) and the amount of soluble sugars in leaves (P-value <0.001). These results showed that the osmotic adjustment through increases of soluble sugars in leaves, decreased the leaf water potential and increased drought resistance in this plant, although this ability is low. With these conditions, this plant could not be considered as drought-resistant plant.