The simulative crop coefficients in each growth period of winter wheat were calculated by the potential and actual evapotranspiration of winter wheat during the whole growth period that both simulated with crop growth model. These simulative crop coefficients were compared with the standard crop confidents at different growth stages provided by FAO and the comparison results verified the accuracy of their values and trends. The experience logarithmic model was built based on the leaf area index obtained by both point-based measurement and remote sensing inversion method. The continuous daily regional crop coefficient could be calculated by remotely sensed leaf area index. The ratio of simulated crop coefficient and daily regional crop coefficient could be used as an optimization factor for evapotranspiration model and the evapotranspiration results of simulative crop coefficient before and after optimization in the whole growth period during 2013—2014 in Guanzhong Plain were obtained. Compared with the point-based measured data, it was found that the maximum relative error was reduced to 9.89% from 14.36% after optimization. So the optimized evapotranspiration reversion model was more accurate than the model without optimization, especially under the condition of low plant coverage. The accuracy showed a significant improvement.