Abstract: Based on the annual and seasonal mean temperature data of 135 stations over the five provinces in Northwest China during the period of 1960 to 1990, the distribution of annual mean temperature is divided into four regions with the significance level of 0.001 by the fuzzy classification method. They are the north part of Xinjiang; the most parts of the area in Northwest China; the Qaidam basin; and the upper streams of Yangtze and Yellow Rivers, respectively, Furthermore, the temperature sequences of the year, winter and summer for the four areas are set up, and the variation of temperatures for the recent several decades in Northwest China is analysed