The Schistosomiasis is a serious diseases threatening human being’s health. Oncomelannia hupensis is the only intermediate host of Schistosome, and is the most fragile during its life cycle. To effectively control the occurrence of Schistosomiasis and protect wetland and water resource, it is an essential practice to destroy snails of O. hupensis. In the present study, cardiac glycosides were extracted from fresh leaves of Nerium indicum Mill and effects of the cardiac glycosides on mortality of O. hupensis were investigated. Six concentrations of the cardiac glycosides (5, 10, 15, 20, 25，30mg/L) were used to treat O. hupensis, and treatments of O. hupensis with 1mg/L niclosamidum and dechlorided water were set as control. O. hupensis that had been treated with varying concentrations of cardiac glycosides for 1～5d was randomly chosen for testing the mortality after 1d incubation in water following thoroughly rinsing with dechlorided water. O. hupensis that did not respond to needle puncture as observed under a dissecting microscope was defined as death. Our results show that the cardiac glycosides obtained from fresh leaves of N. indicum effectively killed O. hupensis. The mortality of O. hupensis treated with 20mg/L cardiac glycosides for 3～4d was similar to that treated with 1mg/L niclosamidum for 2～3d. Statistical analysis revealed that the LD₅₀ and LD₉₀ values for the cardiac glycosides were 4.0500mg/L and 22.2500mg/L, respectively. Fifty O. hupensis treated with the LD₅₀ concentration of cardiac glycosides was used to do PAGE test. The treated samples displayed higher activities of enzymes than the controls; the color of enzyme bands was enhanced and new enzyme bands were induced after 6h treatment. However, the color of enzyme bands was lower than that of the controls, and eventually disappeared after 12 and 24h treatments. There was a marked decrease in glycogen content (ranged from 9.9% to 32.6%) in response to treatments with the cardiac glycosides. The protein contents were not significantly changed by the treatments. This paper analyzed the molluscicidal activity of cardiac glucosides extracted from N. indicum and elucidated the mechanisms underlying the allelopathical effects of the cardiac glucosides on morphological pathology, metabolisms of sugar and protein of O. hupensis. We have obtained chemiecological evidence that N. indicum is capable of killing O. hupensis. These results provide the foundation for developing new plant molluscacide, and scientific grounds for synthesizing biomimetic molluscacide and constructing plant community to destroy O. hupensis.