Abstract: Combining spatial large-scale survey and selective plot investigation, we examined the distribution and diameter at breast height (DBH) of Populus euphratica trees in 100 hm2 of the Argan transect in the lower reaches of the Tarim River, NW China. Within 20 m of the river, the proportion of young trees with DBH<4 cm was the greatest, at 13.24%. With increasing distance from the river, the proportion of young trees gradually dwindles. DBH distribution is simple; the proportion of trees with DBH ranging from 16 to 36 cm is the greatest in the forest. In addition, the further from the river, the higher the proportion of the over-mature forests and effete forests, with DBH > 48 cm. Within 200 m of the river is 80% of the popluar forest of P. euphratica trees with high vitality, with crown density 0-50%. From 200 to 400 m of the river, the proportion of over-mature forests and effete forests with trees of crown density between 50% and 75% and lower vitality begins to increase. At more than 400 m from the river, the density of P. euphratica begins to decrease greatly , with the proportion<5%.