Abstract: In this study 246 tree cores were obtained from 109 Larix sibirica trees at four sites (named as AKL, TEA, TZB and BLS) at the upper treeline in the Altay Mountains, northwest China. The correlation coefficients between the treering width chronologies and climate signals revealed that the correlation coefficient between the BLS and TEA chronologies was the highest (R=0.411, P<0.01). The synchronization of the highfrequency domain was higher than that of the lowfrequency domain in the four standardized treering width chronologies. The climate response of the treering width chronologies from the upper treeline in the Altay Mountains revealed that the main factor affecting the growth of tree rings from the AKL chronology in the northwest Altay Mountain was temperature; that in the TEA and TZB chronologies from the central Altay Mountain was precipitation, and then temperature; and that in the BLS chronology from the southeast Altay Mountain was precipitation. From the northwest to the southeast of the Altay Mountains, the effect of temperature on the growth of tree rings at the upper treeline was gradually decreased, but that of precipitation was gradually increased.