Abstract: With the monthly observation of thundering days in Tibet Autonomous Region (TAR) during 1980~2009, this paper investigated the temporal and the spatial distribution of thundering days and its influencing factors in last 30 years.Results show that thunderstorm generally occurs in the Nagqu region of TAR, and it decreases from the above region to the southwest and southeast parts of Tibet, and the thundering center is different during the different seasons. Summer has the maximum thundering days, followed by that in autumn and spring while winter has the least thundering days. Generally annual and seasonal thundering days have the decreasing variation trend, especially after 2000. Year 2003 is the brake point and the number of thundering day decreases quite obviously since then. The number of thundering days is negatively related with air temperature while it positively related to wind speed, relative humidity and precipitation. The increasing temperature is might be the major climatic factor which results in the decreasing thundering days.