In this research,we did some field survey for Populus euphratica and Tamarix chinensis in the lower reaches of Tarim river. We established a relational model between the coverage of two species and groundwater level according to the Lognormal distribution model; then,simulated the potential coverage used for the frequency of water conveyance and the changes of groundwater level. The results were as follows:1) The optimum groundwater level and the average groundwater level of Populus euphratica is 2.43m and 4.58m respectively, what to Tamarix chinensis is 2.31m and 3.53m. 2) The results,calculated by model,is corresponded with that at Ejin Banner in Heihe river basin. Therefore,this model has a high degree of accuracy,and some definite practicability. 3) In the study area,the potential coverages of Populus euphratica and Tamarix chinensis,may mainly affected by human activity and climate changes,are of 16.98% and 17.24% respectively,has some differences to survey results.