Abstract: A nonwater stress evapotranspiration model (NWSE) was constructed to estimate evapotranspiration. NWSE model was verified with experimental data of maize field. The simulated surface soil and leaf temperature is compatible well with the observed one, which shows that NWSE model is valid. Both NWSE model and PenmanMonteith formula were employed to estimate the maximum evapotranspiration (ET_m) of winter wheat with serial daily mean meteorological data. Comparison shows that during the period of small LAI value, difference exists between the ET_m of PenmanMonteith formula and NWSE model. The difference disminishes as LAI increases.During the high LAI value period, the difference is negligible.