A pot experiment in the outdoor was conducted to investigate the effect of soil progressive drought on the growth and physiology activities of two-year-old Populus euphratica seedlings in the lower reach of Tarim River.The seedlings were grown under well-watered and progressive water deficit conditions with controlling the water supply, respectively.Height, stem base diameter , chlorophyll a and b, superoxide dismutase activity and other physiological parameters were measured during the experiment .In six days of saturated irrigation ( watered until soil water drainage occurred from the bottom of the pot), the soil moisture content decreased to mild drought stress level, and it reached to severe drought stress level in fif-teen days after saturating irrigation in July in the lower reaches of Tarim River.Water deficit in soil consequently affected physiological activities and growth of seedlings to various extents depending on the level of soil water content .In the process of soil water declining from saturated to severe drought levels, increasing soil drought resulted in decreases in the height, stem base diameter, number of lateral branches, the contents of chlorophyll a, chlorophyll b and peroxidase activi-ty, but there were no significant changes in the content of proline and malondialdehyde , chlorophyll a/b value and SOD activity.%采用直径为30 cm、高度为50 cm的PVC管进行室外盆栽试验的方式，研究自然环境下2年生胡杨实生幼株高度、叶绿素质量分数等指标在21 d的土壤渐进式干旱后的变化情况。结果表明：在7月的塔里木河下游，在饱和灌溉6 d后，盆栽胡杨幼株试验的土壤0～40 cm平均含水量就从田间持水量下降至轻度干旱胁迫水平，第15 d后下降至重度干旱胁迫水平。土壤干旱显著降低叶片中叶绿素a、叶绿素b质量分数，过氧化物酶活性显著下降，但叶绿素a/b、脯氨酸、丙二醛质量分数及超氧化物歧化酶活性无显著变化。土壤干旱抑制了胡杨幼株高度、基径的增长和侧枝的萌发，相对停灌后期（7～21 d）而言，停灌初期（0～6 d）土壤水分减少对胡杨幼株生长的抑制作用较小。
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