Lack of water supply for nearly 30 years has caused seriously degradations of Populus euphratica population in lower reaches of Tarim River. The ability of clonal growth of P. euphratica and their relationship with underground water level, the distribution and activity of lateral root of P. euphratica in 100 cm soil depth were investigated in three sections: Yahepu, Yingsu, Alagan along Tarim River. And the external condition for restoring P. euphratica forestry was also analyzed. It is indicated that the lateral roots within 100 cm soil layer was diminished after long term shortage of water supply. Within a distance of 50 m to the river bank, there are some lateral roots which have the ability for clonal growth. The amount of lateral roots became less, the depth of topside lateral roots move down and the reproductive activity of lateral roots decreased when the distance increased from 50 m to 150 m to the river bank. The risk for clonal growth of P. euphratica increased with the increase from original place of water accumulation. When the distance is more than 250 m to the bank of river, there are nearly no hope to clonal growth because of lack of lateral root. Moreover, the micro landforms near P. euphratica are complicated, which made it difficult to irrigate the tree for further clonal growth.