Abstract: The aim of the present study was to investigate the effect of physical modification on the properties of insoluble dietary fiber from oat bran, which might be theoretical basis for further research on the health function of insoluble oat bran dietary fiber. The physicochemical properties of oat bran insoluble dietary fibers, including specific area and particle size, oil holding capacity, water holding capacity, swelling degree, suspension viscosity and cation exchange capacity, were analyzed under the treatment of 500 MPa 20 min 60 ℃ ultra high pressure, 1500 W 30 min ultrasonic and ultra high pressure with ultrasonic.Results showed that the physical modification of ultra high pressure with ultrasonic was significantly more effective than the separate treatment of ultra high pressure or ultrasonic ( p < 0.05) . Taking 1% oat bran IDF as an example, the both treatment of ultra high pressure with ultrasonic treatment can significantly ( p < 0.05) increase the specific area of 13.49 times, holding oil capacity 2.92 times, swelling degree, viscosity and cation exchange capacity of the oat bran insoluble dietary fiber, and reduce fiber size 2.8 times and water holding capacity 2.25 times ( water holding capacity was taking 16% oat bran IDF as an example) .Therefore, it was considered that the physical modification would increase the comprehensive utilization of oat bran insoluble dietary fiber, increase the added value of agricultural products and reuse the food resources.