To study the antioxidant and lower postprandial blood glucose activities by different solvents extracts from Sargassum fusiform, the ethanol extract of Sargassum fusiforme was fractionated by different organic solvents (Petroleum ether, dichloromethane, ethyl acetate, butyl alcohol, PE, DCM, EAC, NBA). The contents of phenols and flavonoids were measured, then the DPPH·, ABTS·, and FRAP methods were used to evaluate the antioxidant activity, the p-nitrophenyl-α-D glucopyranoside (PNPG) and DNS methods were used to determine the inhibition rate of α-glucosidase and α-amylase. Finally, glucose tolerance was measured to evaluate the effect on the postprandial blood glucose. Result showed that EAC extract exhibited the highest total phenols and flavonoids contents, which were 34.47 mg/g and 5.77 mg/g, respectively, and its antioxidant activity was only slightly lower than that of NBA extract in DPPH test, when the concentration was 1.6 mg/mL, the antioxidant activities of EAC extract were 90.17% (DPPH·), 0.35 mmol/mg (ABTS·) and 0.72 mmol/mg (FRAP); in the α-glucosidase inhibition experiment, the IC50 of PE, DCM, EAC extracts were 0.54, 0.29, and 0.27 mg/mL, respectively. The first three extracts can significantly reduce postprandial blood glucose. This study shows that EAC extract has the potential to be used as a dietary supplement or anti-diabetic medicine, providing a theoretical basis for the development and utilization of Sargassum fusiforme.