Spring waterlogging disaster seriously affect the growth and yields of winter wheat in South China. In this paper, a waterlogging index model of winter wheat is constructed by using the Logistic curve equation based on downscaling amended cloudmoist coefficient. According to the critical index value, the sustained days of rainy weather and the potential yield reduction rate of winter wheat, spring waterlogging disasters are divided into three levels. Then, the model is retrieved by using daily meteorological data from 59 stations in Jiangsu Province from 1961 to 2010. The results show that the waterlogging index are negatively correlated to the relative meteorological yields of wheat. With the increase of waterlogging index, the yields decrease. In wet years the disaster of waterlogging would occur one to three times (87.1%), and the least was 5 times (1.9%). Finally, the waterlogging index model is applied to the 2014 spring waterlogging disaster, achieving good result.