To improve the physicochemical and functional properties of oat bran dietary fiber (ODF) and the comprehensive utilization of oat bran, dynamic high-pressure microfluidization (DHPM) was utilized to treat ODF at different pressures. The particle size, physicochemical, functional and probiotic properties of the ODF samples were analyzed to investigate the modification effect of DHPM. After DHPM modification, the microstructure of ODF was broken, the particle size decreased and the specific surface area increased, with the best effect under 420 MPa pressure treatment. The structural breakage and the increase in the specific surface area of ODF may led to the enhancement of its physicochemical and functional properties, and it had greater advantages in terms of the water retention capacity (2.13 ± 0.01 g/g), oil retention capacity (8.46 ± 0.07 g/g), bile salt binding capacity (52.67 ± 1.21 mg/g) and cholesterol binding capacity (1.03 ± 0.02 mg/g). cholesterol binding capacity (1.03 ± 0.02 mg/g). Meanwhile, ODF also remodelled the gut microbiota of the obese population and increased the relative abundance of beneficial bacteria. In conclusion, DHPM treatment effectively enhanced the physicochemical and functional properties of ODF and broadened its applications in the food industry.