The change of potential evapotranspiration has important significance for water cycle and energy balance. In this researchthe daily climatic data of 20 weather stations on the upper Min River Basin and peripheral areas from 1961 to 2000 were used to calculate potential evapotranspiration by using Hargreaves model which was corrected based on the terrain and climate conditions of Sichuan. The characteristics of time series range of PE was analyzed by Mexican Hat Wavelet and Mann - Kendall abrupt change test. The results showed that: it had upward trend from northwest to the southeast in the upper Min River Basin; the annual potential evapotranspiration was quasi - periodic oscillations of 12 years; it had an obvious upward trend since the 90's. The upper Min River Basin had distinct warming and drying trend,especially in the recent 20 years,the worse trend of arid and warm was serious threat to the ecological environmental safety.