Based on the meteorological data and the tree-ring data of Populus euphratica from the upper reaches of the Tarim River, the radial growth of P. euphratica and its correlations with climatic factors were analyzed. The sensitivity of radial growth of P. euphratica to temperature was investigated. The results showed that: ① In the past 170 years, the curve of tree-ring growth of P. euphratica was bimodal with a low value,and the two peaks occurred in 1857 and 1879 respectively. After 1879, the tree-ring growth was in a significant downward trend,and the lowest value occurred in 1955. After that, the tree-ring growth began to increase but decrease slightly after 1989; ② The tree-ring index was negatively correlated with the average temperature from June to September,which indicated that temperature was the main factor affecting the radial growth of P. euphratica in upper reaches of the Tarim River. The radial growth of P. euphratica was in a decrease trend with the increase of temperature; ③ The sensitivity of radial growth of P. euphratica to temperature change was different. The sensitivity of radial growth of P. euphratica to temperature was high at first and then low,and the most sensitive temperature of radial growth of P. euphratica was 18.6 ℃. So it was considered that 18.6 ℃ was the most optimal temperature for the growth of P. euphratica.