Sargassum, one of the most prevalent seaweeds in China, is also the only onewith a high content of fucoidan, laminaran and algin among all the marine algae inChina. Therefore, the utilization of the seawed is obviously important for our country.In order to furnish some basic data to the seaweed industries, methods for the extrac-tion and isolation of mucilage have been studied.The samples were collected in Huilai Xian, South China. The algae was analysedon dry basis it contains 5.1% of laminaran, 6.1% of fucoidan and 21% of alginicacid.Methods of extraction and isolation: Dried seaweed was extracted with a dilute HClsolution at a constant temperature for a definite time. The extract was then filtratedand washed. Crude fucoidan was precipitated at 50% alcohol. Crude laminaran wasobtained at 80% alcohol. Alginate was extracted from the residue with alkali.The optimum conditions for extraction, consists of stirring for two hours at 70℃with HCl solution at pH 4.Purification: By dissolving one part of crude fucoidan in ten parts of distilledwater and then one part of 4M CaCl_2 solution was added. After centrifugalized, thesupernatant was fractionally preciptated with 30% and 60% of alcohol pecipitation in30% alcohol was impurilles nd in the 60% fraction was fucoidan.On part of crude laminaran was dissolved in five parts of water, and fractionallyprecipitated in 50% and 80% alcohol and in the 80% fraction was Iaminaran.The yields are fucoidan (containing 44. 7% of fucose) 3.9%; laminaran (contain-ing 91% of glucos) 3.1% and sodium alginate 17.8%.