Abstract:The evapotranspiration of the cropland is the sum of plant transpiration and soil evaporation. Assessment of actual evapotranspiration of crops is very important for the water saving technology, water resource management and reasonable irrigation plan. In this paper, the actual evapotranspiration of summer corn measured by automatic weighing lysimeter during the growing season (April to September) in 2013 is used to evaluate the applicability of Penman Monteith (FAO P M), Hargreaves, and Priestley Taylor methods in the Huailai Region of Hebei Province. Correlation coefficients, the root mean square error (RMSE), consistency index (d) and other indicators are applied, in monthly and daily time scales, to compare the accuracy of the three methods. The results show that: （1） compared with lysimeter measured results, summer maize monthly actual evapotranspiration calculated by the three methods have some deviations; FAO P M method and Hargreaves method show good performance and accuracy; the accuracy of P T method is the worst. （2） The main meteorological factors that affect the actual evapotranspiration calculation results are the net radiation of the sun and temperature. （3） The Hargreaves method needs fewer parameters and has a great advantage in computing, and it is credible in assessing actual evapotranspiration in Huailai.