Abstract: Abstract: Grain yields of rainfed winter wheat in the Huang-Huai-Hai Plain are often low and vary substantially from season to season. In the past several decades, amount of precipitation in the Huang-Huai-Hai Plain has fallen dramatically. By contrast, agricultural water consumption is so great that water resource is insufficient, leading to excessive exploitation of underground water, in which case irrigation water is far from enough. Under the backdrop of great climate changes, lack of irrigation water and severe drought will have potential impact on winter wheat yield. Simulating the effect of drought on winter wheat has been identified as an important contributor to agricultural production in such environments. In this paper, based on meteorological data and field observations of 6 typical meteorological stations from six agricultural sub-regions of the Huang-Huai-Hai Plain from 1981 to 2010, the yield reduction rate of potential drought in critical growth stages of winter wheat was determined in the Huang-Huai-Hai Plain. Then the probability distribution of yield reduction of 6 typical sites and the relationship between variation of soil moisture and yield in typical wet and dry years were analyzed. The results showed that the regional simulation capability was acceptable and the 3H could be the representative variety of winter wheat in Huang-Huai-Hai Plain for simulation. Regional distribution of yield reduction rate was gradually growing serious from south to north in jointing-heading stage, and the yield reduction rates in agricultural region I, Ⅱ and Ⅲ were more than 40%, and in Region Ⅳ, Ⅴ and Ⅵ were 38%, 27% and 13% respectively. The regional distribution of yield reduction rate of each agricultural region was mainly caused by the climatic factors. In addition, the probability of the same level of yield reduction rate in jointing-heading stage was much larger than that in filling stage. The probability of the same level of yield reduction rate in northern region was much larger than that in partial southern area. In the drought years, irrigation was needed to provide water for the soil surface layer to meet the demand of winter wheat. If drought happened in the jointing-heading stage and the deep-layer soil water was insufficient, the wheat had to rely on irrigation to provide sufficient water for its later growth stage. If drought happened in the filling stage, the wheat root systems had to grow down deeper to get more water, which would cause the reduction in the wheat yield. China has insufficient water resource, which is especially true in North China. The limited water resource should be applied in critical regions and stages. Water saving and drought prevention are a long-term task. Prediction shall be made on water stress in key growth stages and simulation analysis shall be performed on crop models to determine potential yield reduction due to drought, thereby to make reasonable and scientific irrigation measures. This will have referential value for evading drought risks and developing water-saving agriculture under climate changes. The results are expected to provide basic information for drought management and rational irrigation of winter wheat in the Huang-Huai-Hai Plain by focusing on the potential drought in critical growth stages of winter wheat.