Abstract: To investigate the applicability, temporal and spatial variability, and the influencing factors of the potential evapotranspiration calculation methods in the Qinling-Daba Mountains, the main part of the north-south transitional zone in China, four different potential evapotranspiration estimation methods were selected, and compared to investigate their applicability in the north-south transitional zone in China, using the FAO56 Penman-Monteith (P-M) method as a benchmark. Based on the estimation results obtained by the P-M method, the spatial and temporal distribution characteristics of potential evapotranspiration in the Qinling-Daba Mountains were studied and the effect of elevation on potential evapotranspiration in the Qinling-Daba Mountains was analyzed by using the Mann-Kendall trend test. The results showed that the Priestley-Taylor (P-T) method was the best, the Hargreaves (Har) method was the second, and the Thornthwaite (Tho) method was the worst among the selected estimation methods. The minimum value of annual potential evapotranspiration in the study area was 800 mm at Dujiangyan station, and the maximum value was 1 120 mm at Sanmenxia station; the seasonal potential evapotranspiration in the study area was the highest in summer (330~430 mm) and the lowest in winter (100 mm); the annual potential evapotranspiration (PET) showed a gradual increase from southwest to northeast; the maximum value of Z value (4.43) obtained from the M-K trend calculation of annual potential evapotranspiration was at the Hezuo station, and the minimum value (−4.77) was at Sanmenxia station. In general, the annual potential evapotranspiration (PET) in the northwestern part of the study area showed a significant increasing trend, while the southeastern, northeastern, and central-northern areas showed a significant decreasing trend; the evapotranspiration at each station decreased with increasing altitude, but the effect of altitude on evapotranspiration gradually decreased with time.