Abstract: A compare experiment is set to study the Evapotranspiration of eucalyptus in Guangdong Province. Remote sensing image (Landsat TM) is used to retrieval evapotranspiration of eucalyptus forest and natural mixed forest based PT-T and SBDART model. The experimental final results show that: 1）regional evapotranspiration and vegetation index （NDVI） are positive correlation in both types of forests; 2）On the same geographical and environmental conditions, the eucalyptus forest region has a stronger evapotranspiration phenomenon than natural mixed forest region. When the NDVI was 0.4, the difference of 24 hour ET is about 0.18mm.The research notes that the eucalyptus forest still has growth vigor in humid climate areas of Guangdong. The region of the eucalyptus forest will consumes more water with the fast growth process than the natural mixed forest, and further impacts on the process of regional water circulation.