The process of steam explosion assisted superfine grinding (SESG) on yield and particle size properties of wheat bran(WB) powder was evaluated. Then the chemical components, physico-chemical properties of different particle size WB powders (of 425-212, 212-100, 100-75, <75 mu m) were investigated. SEM, FTIR results confirmed that steam explosion had the effect of breaking the cell wall of WB. SESG significantly increased by 49.09% yield of <75 mu m powder than untreated superfine powder. Compared with the others, SESG powder (of <75 mu m) showed higher values in water solubility index (211.75 mg/g), oil holding capacity (1.68 g/g), bile salts and cholesterol adsorbing capacity (1.31 and 21.87 mg/g). And it had more total phenolic and total flavonoids content (7.27 GRE/100 g and 378.97 mu g CE/g), which showed the strongest DPPH radical scavenging activity (87.68%). SESG processing will offer a new approach for fiber materials superfine powder preparation, and SESG powder (<75 mu m) could be widely used in food products. (C) 2020 Elsevier B.V. All rights reserved.