By comprehensive analyses, it was found that the variations in δ18O recorded in Malan ice core from the Kekexili Region on the Tibetan Plateau could represent the changes in air temperature during the summer half year (from May to October) over the Kekexili Region and the northern margin of the Tibetan Plateau. The general increase trend in δ18O in this ice core during the past century indicated climate warming, and it was estimated that air temperature during the summer half-year rose about 1.2℃over there then. However, this ice core record documented that the study area has been cooling while most of the world has been dramatically warming since the late 1970s. A teleconnection was found between the variations in δ18O in the Malan ice core and the North Atlantic Oscillation. Moreover,the variations in δ18O in this ice core were similar to that in the summer half-year air temperature over the southern Tibetan Plateau on the centurial time scale, but opposite on the multidecadal time scale.