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The inter-annual stable carbon isotope ratio (δ¹³C) of three tree-ring cores of P. euphratica (<i>Populus euphratica</i> Oliv.) was determined from Ejina Oasis in Northwest China. A robust and representative δ¹³C chronology is generated from the three δ¹³C series using an arithmetic mean method. After eliminating the influence of the δ¹³C from elevated atmospheric carbon dioxide (CO₂) concentration, we obtained a carbon isotopic discrimination (Δ¹³C) chronology. According to the significant correlation between the tree-ring Δ¹³C and instrumental data, we reconstructed the mean maximum temperature anomalies from previous December to current September (T_DS) for the period 1901–2011. The reconstruction explained 43.6% of the variance over the calibration period. Three high-temperature periods (1929–1965, 1972–1974, and 1992–2006) and three low-temperature periods (1906–1926, 1966–1968, and 1975–1991) were found in the reconstructed series. Comparisons between the reconstructed T_DS and the observed mean temperature from previous December to current September in Anxi meteorological station and the temperature index in north-central China demonstrated the reconstructed T_DS has the advantage of reliability and stability. The significant spatial correlation declared that the reconstruction has a broad spatial representation and can represent the temperature variation characteristics in a wide geographical area. In addition, we found that the area of Ejina Oasis is smaller (larger) when the mean maximum temperature is higher (lower), which may be due to a conjunction effect of natural and anthropogenic activities. Significant periodicities and correlations suggested that the T_DS variations in Ejina Oasis were regulated by solar radiation and atmospheric circulations at the interannual and interdecadal time scales.