On the basis of the trend influence of ecological hydraulics characteristics of Oncomelania and variation of flow regime on the environment variation of Oncomelania breeding grounds in epidemic area, the flow regime indices are put forward to characterize the breeding environmental conditions of Oncomelania Hupensis Gredler. Taking the Dongting Lake with most widely distributed Oncomelania Hupensis Gredler and most serious schistosomiasis epidemic situation in China as an example, the size of Oncomelania Hupensis Gredler breeding grounds in recent years is deduced from analysing the variation of flow regime in Dongting Lake, and the response relation between the area of Oncomelania Hupensis Gredler breeding grounds in Dongting Lake and the mean water level at Chenglingji Station during flood season is revealed. The research shows that the relation is remarkably linear. The results are not only helpful for the forecast and prevention of schistosomiasis epidemic situation, but also for the technical service of the spot check and kill off of Oncomelania Hupensis Gredler.