【Objective】To compensate a lack of historical data of underground water level in the Lower Tarim River and provide a new method for reconstructing historical changes of underground water level in the arid inland river basin. 【Method】Populus euphratica,a dominant species of desert riparian forest,was studied. A total of 58 tree rings were cored from 29 P. euphratica trees in Yingsu section of the Lower Tarim River in September,2015.48 cores were selected using software of Cofecha and Arstan to set up the width chronology of P. euphratica. The change trends of chronology and underground water level were analyzed by moving-t test,Mann - Kendall trend test and cumulative curve. Relationships between tree ring width and temperature,precipitation,underground water level were analyzed using the Frequencies, one-way ANOVA,Pearson Correlation and Regression Models. 【Results】The tree ages of P. euphratica ranged from 40 - 80 years. Rotten xylem usually occurred when P. euphratica was more than 60 years,and no more than 100 years old P. enphratica with healthy xylem were found in the Yingsu section of Lower Tarim River. Step change point of standard chronology of P. euphratica was 1957,1967,1975,and 2000,respectively. There was no significant correlation between the regional climate change factors (temperature,precipitation) and chronology of P. euphratica. Main environmental information of tree rings of P. euphratica was the hydrological process. We successfully reconstructed the historical change of underground water levels from 1933 to 2015 using tree ring width of P. euphratica,which was consistent with the historical records of regional hydrological process.【Conclusions】Effects of regional temperature and precipitation on tree rings of P. euphratica were not significant in the Lower Tarim River. Tree ring of P. euphratica mainly carried the hydrological information,so it could be a new index for researching the historical changes of underground water level in the Lower Tarim River.