Abstract: Carotenoids from Scytosiphon Lomentaria were extracted by organic solvent method in this paper. Carotenoids were separated and purified by column and thin- layer chromatography. The major carotenoids from Scytosiphon Lomentaria were analyzed and identified by visible spectrum,infrared spectroscopy and HPLC- MS. The contents of major carotenoids from Scytosiphon Lomentaria were determined by HPLC method. The results showed that the major carotenoids from Scytosiphon Lomentaria were β- carotene and fucoxanthin,which contents were 124.55 μg / g( dw) and 2862.20 μg / g( dw),respectively.