FGS, isolated from the water solution of enzymolyzed laminaria japonica, is a mixture of acid heteroglycans. Four fractions F1, F2, F3, and F4 were obtained from FGS by ion exchange chromatography. After further purified by gel filtration chromatography on a sepharose 2B and 6B column, we obtained F9, F10, F11, and F12. They showed single band when identified by electrophoresis. The molecular weight of F9, F10, F11, and F12 was estimated to be 216, 120, 138 and 140KD respectively. They containedа-glucosidic bond by IR and 1H-NMR analysis. The typical absorption peaks of these polysaccharides were showed in UV and IR spectra. These polysaccharides contained rha, fuc, man, gal, and uronate when identified by paper chromatography (p.c) and gas chromatography (GC). The molar ratio of these sugars was also assayed. FGS, isolated from the water solution of enzymolyzed laminaria japonica, is a mixture of acid heteroglycans. The four fractions F1, F2, F3, and F4 were obtained from FGS by ion exchange chromatography. After further purification by gel filtration chromatography on a sepharose 2B and They showed single band when identified by electrophoresis. The molecular weight of F9, F10, F11, and F12 was estimated to be 216, 120, 138 and 140KD respectively. They containedа The typical absorption peaks of these polysaccharides were showed in UV and IR spectra. These polysaccharides were shown in UV and IR spectra. These polysaccharides contained rha, fuc, man, gal, and uronate when identified by paper chromatography (pc) and gas chromatography (GC). The molar ratio of these sugars was also assayed.