Black-grained wheat bran, as the research subject, was processed by extrusion and microwave-extrusion processing techniques to extract water-soluble and water-insoluble pentosans, and ion chromatography, high performance liquid chromatography and rheometer were used to analyze the changes in the composition and physicochemical properties of pentosans under different processing conditions. After treatment with extrusion or microwave-extrusion, the results showed that the yields of water-soluble pentosans were increased, while the yields of water-insoluble pentosans decreased, and the yields of total pentosans were increased from 5.76% to 6.43% and 11.32%, respectively. The monosaccharide of pentosans consisted of arabinose, xylose, glucose and trace of galactose. Extrusion or microwave-extrusion treatment increased the glucose content, gradually decreased the branch degree of water-soluble pentosans and gradually increased the branch degree of water-insoluble pentosans. The relative molecular mass and viscosity of pentosans gradually decreased following the processing technology, and the content of bound ferulic acid was increased significantly. The study showed that using extrusion and microwave-extrusion processing technology to treat black-grained wheat bran could contribute to increase the yields of pentosans, increase the content of water-soluble pentosans, and further improve the physical and chemical properties of pentosans.