Abstract: Using the mean annual temperature data from 1952 to 1995, the climatic characteristics, interdecadal variation, climate accident, oscillation period, abnormal warm and cold variation trend are analyzed. The results show that there exist three warm periods and two cold periods for annual and seasonal temperature, 1960′s was the coldest decade, the temperature decreasing was most obvious in autumn, and the temperature was higher during the period of mid and last 1980′s and 1990′s. The periods of 22-year, 11-year and 3 or 4-year variation were significant. Climate catastrophes occurred in the early 1960′s and 1980′s. There were more anomalous cold years in 1960′s and 1970′s, whereas anomalous warm years in 1980′s. In 1990′s, the mean annual temperature of most years was anomalous. In addition, the linear trend of the warming for mean annual temperature over Tibet during the last forty years indicated an increase of 0.065 ℃/10a and the greatest warming trend occurred in the spring and autumn of the last 10 years.