Abstract: The jackfruit seed dietary fiber was modified by high temperature cooking combined with ultrasonic enzymatic method. Single factor combined with response surface method was applied to optimize the modification process conditions. The structure of soluble dietary fiber (SDF) before and after modification was compared and analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetry (TGA) and Fourier transform infrared spectrometer (FTIR). The functional properties of SDF before and after modification were determined with water holding capacity, expansion capacity, oil holding capacity and adsorption capacity for nitrite ion, glucose, bile salt and cholesterol as indicators. The results showed that the optimum modification conditions of DF were as follows: The ratio of material to liquid 1:21 g/mL, cooking temperature 121 ℃, cooking time 43 min, cellulase amount 8%, ultrasonic-assisted enzymatic (UAE) power 360 W, UAE temperature 40 ℃, UAE time 52 min. Under these conditions, the yield of SDF was 24.39%±0.03%, the yield of unmodified SDF was 16.93%±0.60%. Compared with unmodified SDF, FTIR results showed that the cellulose components of jackfruit seeds were redistributed. SEM indicated a more porous structure. XRD results showed an increase in crystallinity, and TGA results showed better thermal stability. The water holding capacity, expansion capacity, oil retention capacity, nitrite ion adsorption capacity, glucose adsorption capacity, bile salt adsorption capacity, and cholesterol adsorption capacity of modified SDF were significantly better than those of unmodified SDF (P<0.05). Therefore, high temperature cooking combined with ultrasonic enzymatic method could improve the functional characteristics of SDF in jackfruit seeds and provide a theoretical basis for the modification of jackfruit seed dietary fiber.