Abstract: This study investigated the effects of snailase (SE), cold plasma (CP), and the combined treatment of snailase and cold plasma (SE-CP) on the structure and physicochemical properties of insoluble dietary fiber (IDF) from oat bran. The relationship between the structure and physicochemical properties of IDF was analyzed using scanning electron microscopy, X-ray diffraction, particle size analysis, water-holding capacity, oil-holding capacity, and glucose adsorption capacity. The results indicated that the modification treatments did not significantly alter the functional groups of IDF. After modification, the particle size decreased, the specific surface area increased, and the surface structure became more porous, with the SE-CP treatment showing the most pronounced effect. X-ray diffraction and thermogravimetric analysis revealed that SE and SE-CP treatments increased the crystallinity to 24.3% and 30.6%, respectively, while enhancing thermal stability. Additionally, both SE and SE-CP significantly reduced water-holding capacity (P<0.05), while all three modification treatments improved oil-holding capacity (P<0.05). The modified IDF exhibited significantly enhanced glucose, nitrite ion, and cation exchange capacities, along with a notable increase in the ABTS⁺· and DPPH· scavenging rates in vitro (P<0.05), with the combined modification showing the best results. In conclusion, the SE-CP treatment effectively improved the structure and physicochemical properties of IDF from oat bran, enhancing its physiological activity.