Abstract: In this study,enzymatic preparation with cellulase and α- amylase and ethanol fractionation precipitation method were used to obtain three different okara soluble dietary fiber( SDF- 1,SDF- 3,SDF- 5),and their composition and antioxidant activity were investgated by gas chromatography,infrared spectroscopy,and in vitro evaluation method.The results showed that the total sugar and galacturonic acid content contained in SDF-1 were the highest,53.44% and 20.43%,respectively,while SDF-5 had the highest reducing sugar content of 10.56%.GC analysis revealed that SDF-1 was composed of Ara,Man,Glu and Gal with a molar ratio of 1.21 ∶ 1.60 ∶ 4.90 ∶ 1.33,both SDF-3 and SDF-5 were composed of Rha,Ara,Xyl,Man,Glu and Gal,with a molar ratio of 2.00 ∶ 4.05 ∶ 0.98 ∶0.84∶ 0.96∶ 13.64 and 1.46 ∶ 4.75 ∶ 1.04 ∶ 2.10 ∶ 1.64 ∶ 23.92,respectively. SDF- 5 exhibited the strongest antioxidant activities in three okara SDFs,evidenced by its ability to scavenge DPPH and ABTS radicals,high reducing power.Based on the results above,it could establish foundation for further development and utilization of soluble dietary fiber from okara.