The soluble dietary fiber （SDF） was extracted after pretreatment of bean dregs by irradiation technology. The microstructure, crystallinity and basic structure were observed by scanning electron microscopy, X-ray diffraction and infrared spectroscopy to analyze the effects of irradiation technology for SDF. The yield and water holding capacity of SDF, expansion force, cation exchange capacity, combined hydraulic power, α-glucosidase activity and antioxidant activity were obtained to explore the effect of irradiation technology on its physical and chemical properties. The results showed that the microstructure, the crystallinity, the physical and chemical properties of irradiated SDF were significantly improved compared with the unirradiated bean dreg SDF. The microstructure of irradiated SDF was finer and fluffy, and the crystallinity was improved by 3.78 percentage points. And the extraction rate was improved from 2.36% to 4.15%, the expansion force was increased from 4.24mL/g to 5.36mL/g, the combined hydraulic power was increased from 2.93g/g to 3.21g/g, the water holding capacity was increased by 0.52g/g, the antioxidant capacity was increased by 1.23mmol/g, cation exchange capacity and α-glucosidase activity were also significantly increased. Irradiation affected the physical and chemical properties of the bean dregs by changing the structure of the SDF. This experiment provided a theoretical basis for the study of the mechanism of irradiation on bean dregs SDF and the technology of bean dregs storage, and also provided a method for the extraction of soluble dietary fiber.