Abstract: The extractable lipids were isolated using soxhlet extraction method in the surficial sediment of Taihu lake. The ketones were fractionated on an activated SiO₂/Al₂O₃ column with hexane/ethylacetate (9:1,V/V) solvent. The ketone fraction was analyzed by GC-MS instrument. A series of alkan-2-ones were detected in the sediment samples of Taihu lake. The distribution range of carbon number was C₁₄C₃₃, major peak was C₂₉ with high OEP(odd to even predominance index). 6,10,14-trimethyl pentadecan-2-one between the peaks of C₁₆ and C₁₇ with high abundance was also found. All the ketone compounds were identified by the analysis of their mass-spectrogram, retention time and the standard mass-spectrogram.