Research on basic theory and its application in Agrometeorology is ernphasized in the United States of America,especially laying stress on energy exchange,water exchange,accumulation and change of matter,models in agricultural production,and interaction between plant and environrnent in the soil-plant-atmosphere system. Reserch is conducted in field condition with advanced data collect system. Neutron probe and lysimeter are widely used in measurement of actual evapotranspiration and used to verify the formulas for calculating evapotranspiration. Many methods calculating potential evapotranspiration are developed from Penman equation and developed computer soft wares to match it. Comparing to other equations,modified Penman-Monteith equation is accurate and used widely.