During evolution, plant species developed various mechanisms to enhance their drought adaptation, including physiological adjustment and structural modification. Plants under arid conditions regulate their water status using several tactics such as leaf biochemical and stomata characteristics as well as xylem sap flux. According to the cohesion-tension theory, water moves through the xylem under tension during transpiration and therefore, rapid transpiration during the drought season increases the risk of xylem cavitations. This study was carried out on Populus euphratica Oliv., the main poplar species distributed in arid land of northwestern China. Two-year old seedlings of P. euphratica were cultivated in-situ at the ecological observation station and mature P. euphratica trees selected from the natural stands along the river bank on the lower reaches of Tarim River, southern Xinjiang, China. Xylem hydraulic traits including xylem maximum hydraulic conductivity (k_s(max)), natural embolism level (PLC,%), as well as lateral root anatomical structure were determined. Results revealed that the native embolism level in lateral roots and branches(2≤d<5 mm)of mature P. euphratica trees were relatively higher with mean PLC value of more than 50%. Morning native embolism at branch level (PLC 58%) was lower than in the afternoon (PLC 67%), but there were no significant differences (P>0.05) between the morning and afternoon native branch xylem embolism. The k_s(max) value and native embolism level in lateral roots of mature P. euphratica trees at 200 m from the river bank were higher than those at the river bed, and there were significant differences (P<0.05), between the native embolism level but not the k_s(max) value. With the an increased stress from soil drought, the lateral root native embolism level of P. euphratica seedlings increased while stomata conductance decreased, and there was a significant negative correlation between them (R =-0.9, R = -0.811). Anatomical structure of xylem in lateral roots in the same diameter class(2≤d<5 mm) revealed that mean vessel diameter(d_mean) and mean hydraulic diameter (d_95%, d_h)of mature trees were significantly higher (P<0.01) than that of its seedlings, and seedlings had higher vessel density than mature trees. Maximum hydraulic conductivity were closely correlated with mean vessel diameter and hydraulic diameter in lateral roots (R>0.9). Generally, P. eupratica growing at the arid land had relatively higher native embolism level, which is beneficial since it aids in preventing excessive water loss during transpiration and therefore affects positively the water status of the plant. This study of xylem hydraulic traits and its anatomical structure facilitates understanding of the biological background of P. euphratica and acclimatization to drought environment.