Abstract: In order to better understand the effect of the lake shrinkage on the flood process in a large lake,a quantitative analysis of the relationship between the lake shrinkage and the flooding in Dongting Lake was conducted,for which Jingjiang-Dongting Lake hydrodynamic model was applied and different scenarios of water area in the Dongting Lake were assumed. The results show that the water level and peak discharge will increase,and the peak time will occur earlier with the shrinkage of the lake. The water level in the West and South Dongting Lake would increase by around 2.0 m and the water level in the East Dongting Lake would increase by around 0.4 m if the area of Dongting Lake was shrunk from 2 670 km²to 1 380 km² when the 1996-type flood occurred in Dongting Lake. Moreover,the arrival time of the peak water level at Chenglingji station would be about 11 hours earlier,and the peak discharge would increase by about 4 300 m³/s. Hence,the flood disaster would be more severe in the Dongting Lake area if the lake continues to shrink from now on. In addition,the water surface slope changes a little in the West and South Dongting Lake. But the water surface slope increases a lot near the Lujiao station due to the water level in the East Dongting Lake is affected by both of the lake shrinkage and the water level in Yangtze River.