With the newly-designed high resolution lysimeter  installed in Nanchang County of Jiangxi Province, the observed overland actual evapotranpiration (ET_a) from September 1, 2007 to August 31, 2008 is used to validate three daily ET_a model, i.e. CRAE (Complementary Relationship Areal Evapotranspiration), GG (Granger-Gray) and AA (Advection-Aridity) models  on different time scales, and the model error is also discussed. The results show that the observed annual average ET_a is 746.1 mm, while the error of calculated ET_a by models with the original parameters is quite large. Calculated ET_a of the three models is smaller than the observed value in dry condition and larger than the observation in moisture condition. The models with calibrated parameters show better predictability than the original ones, yet the improvement in daily calculation is limited. Calculation on a 7-day time scale is remarkably better than daily values: there is a systematic error for AA model, and RMSE of CRAE model is fairly large, yet GG model is relatively the best. According to the comparison with the observations of the  lysimeter, locally calibrated models would show reliable results on 7-day or longer time scale. The above-mentioned research is of great importance in full  understanding of ET_a process, of predictability of models on different time scales and of the water cycle character under climate change condition.