Evapotranspiration is the main dissipation of water resources in arid inland river basin.Future potential evapotranspiration (ET_0)prediction can provide basic data for water resources optimization and management under climate change in the Heihe River Basin (HRB).Three processes could be classified in this study.Firstly,ET_0 was calculated by FAO-56 Penman-Monteith equation based on metrological data from 1960to 2014in HRB.Secondly,future ET_0was predicted by statistical downscaling and deviation regulation based on NCEP reanalysis data from1960to 2014,and CMIP5 CNRM-CM5 model from2006to 2100 under RCP4.5 and RCP8.5 pathways.Finally,three subareas were divided by rotated empirical orthogonal function (REOF)and future trends were analyzed by Mann-Kendall tests for the three subareas and whole HRB.The conclusions showed that:(1)The stepwise regression statistical downscaling models built by NCEP reanalysis data and calculated ET_0from1960to 2014 were suitable for predicting future ET_0of HRB by CNRM-CM5 model simulation and deviation regulation.(2)Annual average ET_0of 20212050,20712100 would increase 3.49%,6.11%than that of 19712000separately under RCP4.5 pathway,while the percentage were 4.64%,10.07% under RCP8.5 pathway.The increasing amplitude of RCP8.5 was greater than that of RCP4.5.(3)Three subareas of future ET_0 were divided by REOF under both pathways.Insignificantly decreasing trend was detected for area I under RCP4.5 pathway,while the trend under RCP8.5 pathway was significant.Significantly increasing trends were detected for area II,III and whole HRB under both pathways.