Abstract: The Chemical constituents of the absolute oil of Lysimachia foenum-graceum Hance were analysed by GC-MS-DS.Sixty-six chemical constituents were identified among 104 GC spectral peaks.Six chemical constituents were reported first.Major constituents in the absolute oil are made up of aliphatic acids.The tasting and touching toxic tests against fleas were carried on respectively with the extracted solutions of ethy acetate,95% ethanol from the raw powder of L.foenum-graecum Hance.The results showed that the actitve components are focused in the ethyl acetate extracted solution and only 5% diluted ethyl acetate extracted solution is able to kill fleas functionally in the touching tests.