Abstract: The tendency and persistency of potential evaporation in the recent 30 years were analyzed based on the observational data of monthly average maximum temperature, minimum temperature, precipitation, wind speed, relative humidity, and sunshine duration of 9 stations in the Nujiang River basin in Tibet from 1981 to 2010 by linear trend analysis and Rescaled Range (R/S) analysis, as well as the Penman-Monteith model. And the relationships between potential evaporation and influential elements, such as sunshine duration, mean wind speed, and precipitation, were also discussed. The results show that the seasonal potential evaporation decreased during 1981-2010. Also, a negative trend of annual potential evaporation, i.e., a rate of -18.4 mm?(10a)-1 significant at the 95% confidence level, was detected. The results of R/S analysis show that the summer, autumn, winter, and annual series of potential evaporation were persistent and it will assume continuous decrease in future, especially in winter. From the 1980s to the 2000s, the decadal anomaly of potential evaporation was positive in the 1980s, whereas negative in the 1990s and the 2000s. It is thus obvious that the decrease of potential evaporation was mainly caused by the significant decrease of wind speed in all seasons, however in spring it was also correlated with significant increase in precipitation, and in summer it might also be related to decrease in daily temperature range.