Abstract: Penman Monteith（PM）model and Shuttleworth Wallace（SW）model were used to simulate hourly evapotranspiration（ET）in a winter wheat field during the main growing season（March May）.The simulation results were further verified based on eddy flux measurements and the sensitivity of ET simulation to resistance parameters was analyzed.The results showed that ET simulated by PM model and SW model were most sensitive to the change in canopy resistance.Due to the sparse canopy of winter wheat in March，PM model may underestimate ET and SW model was better than PM model in ET simulation.Owing to the dense canopy of winter wheat in April and May，both models were satisfied in ET estimation.In April and May，the accuracy of ET simulated by two models was greatly improved by improving the calculation of effective leaf area index（LAI e）.The correlation coefficient and the index of agreement（IA）for simulated and measured ET were much close to 1，with smaller mean relative error（MRE）and root mean square error（RMSE）.

Key words: Penman Monteith model, Shuttleworth Wallace model, Evapotranspiration, Effective leaf area index, Canopy resistance