Elucidating the driving mechanisms of climate and vegetation evolution on regional evapotranspiration change is crucial for developing sustainable vegetation restoration strategies for water resources in the region. This study took the Beiluo River Basin of the Loess Plateau as the research area. Based on remote sensing and climate data, the spatiotemporal evolution of regional evapotranspiration from 1984 to 2018 was simulated using the PT-JPL Model (Priestley-Taylor Jet Propulsion Laboratory). Using partial correlation and multiple regression analysis, the study explored the driving mechanisms and relative contributions of climate change and vegetation greening to evapotranspiration change. The results showed that: (1) Evapotranspiration in the Beiluo River Basin increased significantly at a rate of 3.11 mm/a (P<0.01); (2) The average annual evapotranspiration was highest in the watershed scrub and lowest in the cultivated land. The annual evapotranspiration rates for different vegetation types were: cultivated land > grassland > shrub > forest land. (3) The leaf area index in the Beiluo River Basin showed a very significant increasing trend (0.02 m2"?" m-2"?" a-1; P<0.01). For climate factors, except for precipitation, the other climate factors (mean temperature, net radiation, saturated water vapor pressure, and wind speed) showed significant increasing trends. On the annual scale, evapotranspiration is positively correlated with leaf area index, precipitation and air temperature, but not positively correlated with saturated water vapor pressure, and negatively correlated with net radiation and wind speed. The relative contribution rates of different driving factors to evapotranspiration in the basin were as follows: temperature (29.9%) > leaf area index (21.3%) > radiation (6.2%) > wind speed (4.9%) > precipitation (1.3%), indicating that climate warming and vegetation greening were the key limiting factors for the increase of evapotranspiration in this area in recent years. The results of this study help to deepen the understanding of climate-vegetation-evaporation interaction process, and have important reference value for water resources management and construction of sustainable ecological restoration strategies for water resources in the Beiluo River Basin and even the Loess Plateau.