[Objective] The spatiotemporal characteristics of potential evapotranspiration (ET₀) under climate change were studied in order to provide scientific basis for researching regional ecological water demand and water resource management.[Methods] Based on the daily meteorological data of Yanhe River basin from 1978 to 2017, ET₀ was calculated by Penman-Monteith method. The spatiotemporal variation characteristics of ET₀ were analyzed by Mann-Kendall trend test and Pettitt test. And the influencing factors of ET₀ change were analyzed by Pearson correlation analysis.[Results] The average annual ET₀ of Yanhe River basin was 923.53 mm, showing an overall upward trend. Monthly ET₀ showed unimodal distribution, and the highest value occurred from May to July. Seasonal ET₀ showed as follows:summer > spring > autumn > winter. ET₀ in summer, spring, and winter showed an upward trend, while it showed a downward trend in autumn. The spring evapotranspiration had the largest rate of change. Spatially, ET₀ increased from the west to the south and then decreased to the southeast. The evapotranspiration at Yan'an station was the highest, and that at Zhidan station was the lowest. ET₀ at other stations except Ganquan station was on the rise. There was an "evaporation paradox" phenomenon in the area around Ganquan station. The dominant factors were sunshine duration, 2 m high wind speed and precipitation. The change rate of ET₀ was higher in the southeast and lower in the northwest. The change rate of Yan'an station was the largest, while that of Ansai station was the least. The variation trend and rate of meteorological factors such as average temperature, sunshine duration, relative humidity, atmospheric pressure, 2 m high wind speed and precipitation were significantly different in time and space. The influence of the same meteorological factor on ET₀ was significantly different in time and space. The combination of different variation trends of the same factor had significant differences in the influence of ET₀.[Conclusion] In general, the change of ET₀ in Yanhe River basin is positively correlated with the change of average temperature, sunshine duration and 2 m high wind speed and negatively correlated with the change of relative humidity, atmospheric pressure and precipitation. The change of ET₀ is the most correlated factor with sunshine duration.