Abstract: Flood effect of flood storage and detention areas is related to the safety of people's life and property. Flood impact assessment of flood storage and detention areas is an important scientific basis for flood risk management, flood diversion decisionmaking and disaster assessment. In this paper, Environmental Fluid Dynamics Code(EFDC) hydrodynamic model, geographic information system (GIS) technology and Python language were used to study the flood effect of the flood storage and detention area around Baiyangdian Lake. The national standard NSDTF-DEM (National Standard of the National Standards of the People's Republic of China Geospatial Data Exchange Format) algorithm with independent intellectual property rights was converted into ArcGIS GRD format algorithm in batch, and the high-precision terrain model of the flood storage and detention area around Baiyangdian Lake was established. The flood diversion process of each storage and detention area under the 50- year, 100- year and 200- year return periods of design flood is simulated. The innundation area, average and maximum inundation depth of each storage and detention area under different design flood are analyzed, and the optimization scheme of flood diversion operation in the storage and detention area around Baiyangdian Lake is proposed.