Abstract: Evapotranspiration is the key link between the atmospheric process and terrestrial hydrological process, which plays an important role in water cycle processes and water balance on the regional/basin scales. However, with the effects of global warming climate and human activities, potential evapotranspiration and its response to meteorological parameters have changed significantly in recent decades across the globe. To accuratelly measurement and estimation of evapotranspiration, investigation of the temporal—spatial variations of evapotranspiration has become an important part of the water cycle in response to global climate change. Therefore, we review the development of the evapotranspiration theoretical methods, evapotranspiration trends and the dominant factors, the temporal—spatial variations of evapotranspiration and sensitivity analysis, and summarize the main estimation models of evapotranspiration. The main methods for calculating and estimatingthe evapotranspiration are hydrologic method, micrometeorological method, plant physiology, remote sensing method and SPAC integrated simulation. We also review and synthesise the literatures to assess the applicability, advantages and disadvantages of the evapotranspiration estimation and measurement methods, to summarize the evapotranspiration trend rates and the influencing factors based on sensitivity and trend analysis. This study will provide an important scientific basis for determining the influence of climate change on water cycle processes and water resources, the hydrological cycle mechanisms of atmosphere—soil vegetation system, agricultural management.