本文通过对近代长江流域钉螺分布及血吸虫病流行的研究，认为近代长江中下游地区由于河、湖泥沙淤积、围垦等因素，天然调蓄防洪能力在下降，使得洪水灾害在近几个世纪一直呈上升趋势，长江洲滩成为钉螺保存地及扩散源，使中下游流域内血吸虫病难以被消灭，而山丘型钉螺则由于残留环境地势复杂，也难以彻底消灭，因此，长江流域血吸虫病的危害在本世纪以来表现十分突出 Based on the studies on the distribution of snail and the prevalence of schistosomiasis in the Yangtze River basin in recent years, this paper argues that in the middle and lower reaches of the Yangtze River, due to the siltation of rivers and lakes, reclamation and other factors, the natural flood control and storage capacity is declining, making flood disasters in recent centuries The trend of the Yangtze River beach become snail conservation and diffusion source, so that the middle and lower reaches of the watershed schistosomiasis is difficult to be eliminated, and the hill snails because of the residual environment topography is complex, it is difficult to completely eliminate, so the Yangtze River basin schistosomiasis Hazard has been outstanding in this century