Located in the north Jiangsu, East China, Lixiahe region is a relatively closed region with frequent flood, it is of great importance to discuss flood changing trend and flooding mechanism for the mitigation strategy in Lixiahe region.Results based on the analysis of the historical flood in the region show that flood types are complex, which have a diverse characteristics, high water level occurs frequently, recently, especially with high reoccurrence interval of flood water level, and frequency of the causative storm is increasing significantly.We view the flooding mechanism of the Lixiahe region a coupling effect of the natural factors and human factors.For natural factors, certainly the storm precipitation plays the most basic role in the flooding mechanism, the bowl-shaped topography is the main background of flood, and the interlaced complex water system makes flood appear more easily.And more, irrational anthropogenic activity is another part for the flooding mechanism, the building of dyke and embankment greatly decreases the lake area, which evidently weakens the capacity of the lake and water body, accumulation of mud resulting from dam construction and the low standard of drainage system makes the continuance of high flooding water level, and the increase of runoff coefficient caused by hydrological effect of urbanization like the increase of imperviousness with the sprawl of urban also leads to great flood in Lixiahe region.Therefore, to ensure the sustainable development for this region, both natural and social factors for flood mitigation should be considered scientifically.