Based on the meteorological data and the winter wheat yield data of 78 weather stations in Anhui Province from 1971 to 2010, the spatiotemporal variation of the water budget during the whole growth period and critical period of winter wheat (from booting to milk ripening stages) in Anhui Province was analyzed using the water budget index. The occurrence of droughts and floods and its impact on the winter wheat yield was also analyzed using the water budget index as the droughtflood indicator. The results showed that the water budget index during the whole growth period and critical period of the winter wheat presents zonal distribution and decreases from south to north. The water deficit occurs significantly in the area north to Hefei and the water supply is adequate in the southern part of the YangtzeHuaihe Area and the region south to this area, with large water surplus in south and small in north. On the whole, the water shortage degree is greater in the critical period than in the whole growth period. The change trend of the water budget index is not significant during the past 40 years. However, the interannual variation of the water budget index is obvious due to the large variation coefficient of the precipitation, increasing the risk of droughts and floods. The drought occurs mainly in the area along Huaihe River and the part north to the river. The frequency of waterlogging is higher in the YangtzeHuaihe Area and the region south. The average yield reduction rates of the winter wheat due to the drought and the flood are 4.2% and 12.4%, respectively. There is a significantly positive (negative) correlation between water budget index and relative meteorological yield in typical drought (flood) year of winter wheat. The medium drought risk of winter wheat is greater in north area than in south area, and the medium waterlogging risk is greater in south area. It is necessary to minimize the planting of the winter wheat in the south area where water is more because the yield loss caused by the waterlogging is greater than the drought.