Abstract: Arabinoxylan were prepared from wheat starch wastewater.The physicochemical properties and antioxidant activity of AX were analyzed by laser light scattering method, IC and in vitro experiments. The results showed that the AX from wheat starch wastewater had a strong reducing ability and a scavenging capacity of DPPH free radicals, while the ability of scavenging hydroxyl radical of AX was relatively weak. Ethyl alcohol fractionation precipitation can effectively separate the AX with different degree of branching, monosaccharide ratio and molecular weight.The AXE ( 60% ethyl alcohol precipitates) had higher purity ( 86.81%) . The galactose ( Gal) content and ratio of Ara/Xyl of AX increased with the increasing concentrations of ethanol, while the molecular weight decreased.The molecular weight, branched structure and monosaccharide ratio of AX played an important role in antioxidant activity.The AX with low molecular weight and a higher degree of branching showed a greater capability to provide hydrogen atoms, while the ability to complex free metal ions was relatively weak.