Schistosomiasis in the Yangtze Valley is mainly distributed in the middle-lower reaches of the Yangtze River,the Chengtu Plains and others.The results of this research show that chemicogeographical environment is the essential ecological factor in epidemic of schistosomiasis.The content of trace element Sr,Ba,Rb,Sc,Cs,F,Th,Pb,Zn,Cd,Sb,Se,La,Ce,Yb,Tb,Lu of water bodies (the water through a filter film,the water without being filtered and sediments) in endemic area is higher than those of nonendemic area.However content of V,Fe,Ni,Mo,As,Hg of water bodies in endemic area is lower than those of nonendemic area.The average continuous multipler index of 31 trace elements of water bodies in endemic area exceeds 1.The molal ratio of Ca to Mg of sediments in endemic area is approximately equal to those (0.8) suitable for the existence of miracidia.