Attribution analysis of changes in evapotranspiration ( ET ) is important for understanding the mechanisms that control ET , which is necessary for reliable modeling and predicting. In this study, we combined eddy covariance methods with the Shuttleworth-Wallace (SW) model to assess the relative contributions of climate and vegetation variables to soil evaporation ( ) and plant transpiration ( ) for an area of maize at Daman Station, and an area of grassland at Arou Station. We quantitatively evaluated the contribution of different potential drivers using partial-differential equations, and found that the available energy at the soil surface and the saturation vapor pressure deficit had the strongest influence on . Although less significant that climate factors, vegetation factors, such as stomatal conductance, had an important impact on for maize and grass. Our results show that changes in the canopy resistance make the biggest contribution to change. Our sensitivity analysis indicates that is most sensitive to aerodynamic resistances from the soil surface to canopy height, and that is most sensitive to surface resistance for the plant canopy, and less sensitive to aerodynamic resistances from the leaf to canopy height. Our study shows that changes in ET were influenced by complex interactions between climate and vegetation variables, and the main drivers for changes in ET were different in different months.