In the arid desert region downstream of the Tarim River, we selected Yingsu, Kaerdayi, Alagan, Yiganbujima four different sections. Through the four typical sections of the underground water level monitoring and calculation, determination of radial growth of Populus euphratica, with the method of mathematical statistics, comparative analysis of different cross section of the radial growth of P. euphratica and the relationship between the groundwater depth, quantitative study of P. euphratica growth reasonable levels, we provided a theoretical basis for the healthy growth and lower Tarim River Populus recovery. The results are as follow: (1) After 2000, the four sections of Populus ring width has increased significantly. Yingsu section has the most obvious changes in tree ring width. Yiganbujima section has the most gentle ring width changes. Before 2000 (to exclude the interference of artificial water), Populus ring index changes are significant differences, the most obvious ups and downs for the Yiganbujima section. Alagan section is the most gentle, Kaerdayi section has a clear downward trend.（2）In four radial sections, Populus growth and significant negative correlation with groundwater level. A regression model of radial growth of Populus and groundwater level found: four sections fit through the 0.05 level to test the equation, fitting better relationship. (3) Populus radial growth decrease with the decline in the four sections of the groundwater level. The sensitivity was first increased, then decreased. Groundwater level corresponding to the maximum sensitivity are: Yingsu section 5.38 m, Kaerdayi section 6.66 m, Alagan section 7.81 m and Yiganbujima section 7.84 m. Populus radial growth in four sections differ in response to the sensitivity of groundwater level changes. Populus growth sensitive groundwater level range is between 5.4-7.8 m.