Potential evapotranspiration (ET₀) is a key variable of hydrological cycle and has important applications to hydrological modeling and crop irrigation scheduling. Under the background of global warming, analyzing the spatiotemporal characteristics of the present and future ET₀ can provide important information for regional water resource management and sustainable agricultural development. To study the impacts of ecological construction and climate change in the past 50 years on the hydrology in the Jinghe watershed, some researches have assessed the changes of ET₀ for the present period; however, almost no study has focused on the potential changes of ET₀. The objective of this study is to project the change of ET₀ during 21^st century on the basis of the current ET₀ analysis and further discuss its impacts on climate in the Jinghe watershed. The data used in this study included daily weather data from 15 meteorological stations, NCEP reanalysis data which reflects the quasi-observed climate condition and GCM grid outputs from HadCM3 under A2 and B2 scenarios. Penman-Monteith (PM) method and statistical downscaling model (SDSM) were used to calculate ET₀ for the present period of 1961-2005 and project ET₀ for the future period of 2011-2099, respectively. The determination coefficient and Nash–Sutcliffe model efficiency coefficient were used to assess the performance of SDSM. The inverse distance weighted interpolation and nonparametric Mann-Kendall test was used to analyze the spatial distribution and temporal change of ET₀, respectively. Results showed that ET₀ calculated by PM formula correlated to the pan evaporation well, which means that the estimated ET₀ is reliable. With annual average of 934.6 mm for the present period, ET₀ had a spatial difference decreasing from the east to the southwestern part of the Jinghe watershed. An insignificant upward trend of annual ET₀ was detected for the present period and an abrupt change occurred in 1977. The monthly ET₀ distributed as a single peak curve with the greatest and smallest value in June and December, respectively. During 21^st century, ET₀ would greatly increase by 1.9 mm/a and 0.9 mm/a under A2 and B2 emission scenarios, respectively. ET₀ appeared to increase dramatically since 2049 and have an upward abrupt change in 2061. Future ET₀ also varied among seasons with the greatest increase in summer and the least in winter. The spatial distribution of future ET₀ was similar to the current period,but the regional difference would increase over time. The aridity index calculated by the ratio of ET₀ to precipitation revealed that the Jinghe watershed would be threatened by more severe drought during 21^st century, and most regions would have semiarid climate at the end of 21^st century though now it is a transition region with semiarid and subhumid climate. The uncertainties in this study are mainly from GCM and downscaling method; however, as the GCM from HadCM3 used in this study has the best performances in simulating Chinese climate and SDSM has good performances in downscaling the present ET₀, the results should be reliable and will be further validated with more GCM data and downscaling methods. The continuous increase in ET₀ and drought would aggravate the water shortage and further influence the ecological construction and regional development in the Jinghe watershed; therefore, some countermeasures should be adapted in advance to minimize the adverse impacts.