Brown seaweed is regarded as a kind of traditional medicine and its bio-functions are related to immune regulation, anti-inflammation and anti-tumor in science. Previously, our data demonstrated that the efficiency of immune activity was S. hemiphyllum＞L. Japonica＞U. pinnatifida water extract. Thus, S. hemiphyllum water extract was prepared to investigate for the ability to anti-tumor in this year. S. hemiphyllum water extract was obtained 85.30±0.87％ carbohydrate, and fucose (234.48±0.08 μmol/g), mannose (133.74±0.18 μmol/g) and galactose (49.14±0.07 μmol/g) were the major sugar components. Polysaccharide of S. hemiphyllum water extract, as determined by anion-exchange chromatography, showed Peak 1 and 2. Our results indicated that S. hemiphyllum water extract induced HepG2 cells apoptosis involving caspase-8, BID cleavage, BAX activation, Cyt C release and caspase-3 activation. Peak 1 and 2 both could induce apoptosis through a caspase-8, 9, 3 activating pathway, but Peak 1 couldn’t stimulate Cyt C release. Thus, we suggested that Peak 2 of S. hemiphyllum water extract induced HepG2 cells apoptosis through mitochondrial pathway. We prepared three of ethanolic extract from S. hemiphyllum, U. pinnatifida and L. Japonica and investigated their anti-oxidation and suppressive effects on the differentiation of 3T3-L1 cells. S. hemiphyllum ethanolic extract, which contains a high content of total polyphenols, showed strong anti-oxidation and inhibition of intercellular lipid accumulation. In addition, in 3T3-L1 cells treated with S. hemiphyllum ethanolic extract, adiponectin, an anti-diabetic adipokine, was down-regulated in a dose-dependent manner. Further, we focused on the 【acetone: water=7: 3】extract of S. hemiphyllum, it was showed that 【acetone: water=7: 3】extract of S. hemiphyllum had strong inhibition of α-amylase, sucrose and maltase. Therefore, our future work will do the anti-diabetic assay.