Objective To get a molluscicide from Reineckea carnea which is effective on Oncomelania hupensis but has low poison on fish. Methods Methyl soaking, column chromatography and HPLC were used for isolation of molluscicidal component from Reineckea carnea. Results The snail mortality with Reineckea carnea powder was 86.0% for 72 h immersion and 100.0% for 120 h at the concentration of 17.5 mg/L, but the fish mortality was 0 at the concentration of 130 mg/L, indicating that Reineckea carnea had different effects on the two kinds of animals . The fraction A was obtained from Reineckea carnea by methyl immersion, column chromatography. The snail mortality with A was 84.4% for 144 h at the concentration of 10 mg/L, indicating that A had high molluscicidal effect on Oncomelania hupensis. After A being isolated by HPLC, 99.98% RC-Ⅰ was obtained from it . RC-Ⅰ was determined by API2000 LC/MS and other spectrum, and it was deduced to be one of steroidal glycosides. Conclusion Reineckea carnea contains a high effective molluscicidal component.