Abstract:Waterlogging damage is the main limiting factor for stable and high yield of summer maize in Anhui Province. Soil moisture is a direct indicator of agricultural drought and flood conditions. The current density and accuracy of soil moisture observation stations can not satisfy the requirements of drought and flood monitoring, early warning and assessment. To construct a waterlogging index that can reflect the daily changes of soil moisture for summer maize during the seedling stage, based on daily meteorological data, geographic information, and summer maize disaster data of 20 counties (districts) in the northern part of Anhui Province from 1981 to 2020, this paper uses the daily standardized antecedent precipitation evapotranspiration index (SAPEI) in characterizing soil relative humidity. In addition, combined with the industry standard grades of waterlogging for summer maize, the dominant indicators and auxiliary indexes of waterlogging for summer maize during the seedling stage are established. The verified accuracy of the indexes exceeds 90%. The temporal manifestation of waterlogging during the seedling stage of summer maize in northern Anhui is as follows. The most severe period is from 1991 to 2000 and the period from 2001 to 2010 comes the second. 2003 is the year most serious waterlogging in the past 40 years. In spatial distribution, the frequency of waterlogging in the area along the Huaihe River is higher than that in the area north to the Huaihe River. Strengthening the research on monitoring and early warning technology for maize waterlogging and conducting quantitative assessments of regional waterlogging for maize is of great significance to ensure food security in Anhui Province.