Oncomelania-inhibited component in petroleum ether extracts from leaf of Sapium sebiferum (Linn.) Roxb. Was researched by column separation technology and GC-MS method, and compound separated from leaf was identified by NIST 107 and Wiley 6. 0. The results show that relative peak areas of  3,7,11,15-tetramethyl-2-hexadecen-1-ol, hexadecanoicacid, 9,12,15-octadecadienoic acid methyl ester, 1,2-benzenedicarboxylic acid bis (2-ethylhexyl) ester and 8,11,14-eicosatrienoic acid are larger, and suggesting that they are the main oncomelania-inhibited compounds. In which, hexadecanoic acid may be one of active materials inhibiting oncomelania from S. sebiferum. This result has an important value to extension of biological measure controlling schistosomiasis.