Abstract: The paper classifies the methods of estimating regional evapotranspiration into two categories. The one category belongs to hydrology and meteorology, such as water balance, complementary relationship, SPAC, reference evapotranspiration; the other category belongs to remote sensing technique, such as semiempirical model, energy balance, numerical model, absolute RS model. Then several representative ground measuring methods like lysimeter method, Bowen method, eddy correlation method, scintillometer method were summarized. Finally, someexistent problems on estimating regional evapotranspiration by remote sensing were analyzed in brief and the research tendency on estimating regional evapotranspiration was prospected.