Abstract: Based on daily precipitation data at 18 meteorological stations in Tibet during 1961-2010, the authors established annual and seasonal longest continuous dry days time series, and analyzed the distribution characteristics and trends of the longest continuous dry days, and the impact on drought in Tibet, and the preliminary analysis of the possible effect of El Nino on the longest continuous dry days was conducted. The results showed that: the high value region of Tibet’s longest continuous dry days was mainly located in the arid and semi arid climate region, the drier regions were more prone to prolonged weather without precipitation; annual and seasonal longest continuous dry days had a decreasing trend in Tibet, the annual and winter half year exhibited a significant decreasing tendency with the decrease rate of 3.1 d/10 a and 2.8 d/10 a respectively, passed 0.01 reliability test, and the descending mutation occurred in 1977; long time without precipitation was an important cause of drought in Tibet; El Nino played a regulatory role in the longest continuous dry days, the longest continuous dry days had a general increase in El Nino years and a general decrease in the second year of El Nino occurrence.