Winter wheat is mainly planted in water shortage area, such as North China and Northwest China. As a key field management measure, irrigation plays an important role in the production of winter wheat. This paper focuses on the improvement of regional winter wheat yield estimation technique in county scale by adjusting the irrigation management measure in crop growth model. The WOFOST (World Food Study) model was used by dividing the whole county into a number of EMUs (Elementary Mapping Units) and then running the model in each unit in sequence. While running, the measured soil moisture and LAI were used to rate the irrigation parameters. Finally, the calibrated irrigation parameters were used to run the model again. The results showed that the simulated winter wheat growth process was normal. During the whole growing period of winter wheat, the change trends of the time series of soil moisture and LAI were basically consistent with that of the measured. The precision of simulated yield was between 87.26 % and 98.68 % among the 5 units, and the average of the precision was 94.56 %. The precision of simulated winter wheat yield was well, and could meet the needs of winter wheat yield estimation in county-wide. This study may provide basis for estimating crop yield in regional area by using the crop growth model.