Variations in potential evapotranspiration (PET) are closely linked to regional water equilibria and agricultural productivity. Amid the backdrop of ongoing global warming, PET within the arid and semi-arid regions of northern China (ASARNC), notable for its fragile ecological conditions, exhibits non-monotonic fluctuations. In this study, we selected Dali Lake, a hydrologically closed-lake situated in the ASARNC, as the research object. We calculated Delta delta 18OL-P based on delta 18OCarb records (indicative of delta 18OL) and stalagmite delta 18O records (as a proxy for delta 18OP) to reconstruct PET changes since the last deglaciation. The findings indicate a gradual decline in PET from similar to 14 000 cal yr before the present (BP), with PET reaching its minimum around 6 000 cal yr BP. Subsequently, PET exhibited a gradual increase. Moreover, we unveiled an inverse relationship between PET and temperature fluctuations in the ASARNC, suggesting the perpetuation of the evaporation paradox in the region since the last deglaciation. On a millennial timescale, variations in solar radiation (or global dimming) due to changes in cloud or aerosols concentrations, along with shifts in summer wind speed and humidity, rather than surface temperature fluctuations, may primarily drive changes in PET.