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This study quantifies the influences of climate variation and vegetation greening on the changes in evapotranspiration (ET) over 110 humid catchments of China from 1982 to 2016. A process-based model considering climate and vegetation changes is employed to estimateET. The simulatedETcompared well with the observed values based on the flux measurements and water balance equation, with the coefficients of determination above 0.62. During the study period, environmental change of the study area was characterized by the increases in air temperature and leaf area index, that is, climate warming and vegetation greening. AnnualETincreased at 104 catchments with the trends ranging from 0.01 to 6.2 mm yr(-2). The numerical experiment approach and sensitivity method are used to attributeETchanges to climate variation and vegetation greening. The results show that the contributions of climate variation toETchanges estimated by the two methods are 90.6% and 91.3%, respectively, whereas the contributions of vegetation greening toETchanges are only 9.4% and 8.7%, indicating that climate variation controlsETchanges in the study area. However, vegetation greening alters the proportions ofETcomponents, which contributes 59.0%-62.0% to the increase in the ratio of transpiration toET. This study quantifies the roles of climate and vegetation changes in the dynamics ofET, suggesting that more concerns should be paid on the interactions between ecological processes and hydrological cycle in humid regions.