Abstract: This study aimed to prepare soybean dregs insoluble dietary fiber generated from the processing of traditional soybean products (TBP-IDF) and to compare the differences in structure and physicochemical properties between it and insoluble dietary fiber prepared from soybean protein isolate processing by-products (SPI-IDF). The optimal degreasing process of soybean dregs was optimized by single-factor experiments and response surface methodology. TBP-IDF was prepared by a complex enzymatic method and its basic components and fractions were determined. The structural differences between TBP-IDF and SPI-IDF were compared using ion chromatography, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Differences in the physicochemical properties of TBP-IDF and SPI-IDF were analyzed by determining water-holding capacity, swelling capacity, oil-holding capacity, glucose-absorption capacity, and cholesterol-adsorption capacity. The results showed that the optimal defatting process parameters for traditional soybean dregs were as follows: liquid-to-feed ratio of 22:1, treatment temperature of 59 ℃, and treatment time of 70 min, under which the defatting rate of soybean dregs reached 90.13%. The content of TBP-IDF was up to 83.23%, with 29.3% cellulose, 53.5% hemicellulose, and 17.2% lignin. Compared with SPI-IDF, there were significant differences in the composition of the monosaccharides of TBP-IDF, with significantly increased glucose content (P<0.05), but the advanced structure was similar. The water-holding capacity (9.53 g/g) and swelling capacity (5.20 mL/g) of TBP-IDF were significantly higher than SPI-IDF (7.73 g/g, 4.30 mL/g) (P<0.05), while the oil-holding capacity (6.22 g/g) was significantly lower than SPI-IDF (7.95 g/g) (P<0.05). The adsorption capacity of both for glucose and cholesterol increased with the increase of substrate concentration, and there was no significant difference (P>0.05). This study demonstrated that TBP-IDF had similar potential physiological activities with SPI-IDF, which could potentially be used as a functional food ingredient for assisting glycolipid metabolism, and expanded the sources and ways of preparing soybean insoluble dietary fiber.