Abstract: Evaporation is an important process in terrestrial energy and water circle. It is important that evaporation assessment in research of catchments water resource analyses and agricultural production. So it will be widely applied. We summarized the frame and application of Complementary Relationship Areal Evapotranspiration (CRAE) model. The advantage of the model is that it estimate actual evapotranspiration from observations of temperature, humidity and sunshine duration over a wider range of regions without the requirement for factors or assumptions associated with the soil-vegetation system. The result show that the CRAE model seems effective for estimating catchment evapotranspiration.