The sunflower meal was used as experimental object in this experiment， getting water-soluble dietary fiber and insoluble dietary fiber by the method of water extract-alcohol precipitation， and using the ultrasonic modification treatment to compare the physical and chemical properties of SDF and IDF before and after modification， thermal stability and change of the internal microstructure. Results showed that ultrasound modification caused 3.09% and 8.96% increase of the holding water capacity for USDF and UIDF， respectively， whereas led to 23.73% and 17.45% increase of the oil force for USDF and UIDF， respectively. UIDF was superior to IDF on the scavenging effect of DPPH and ABTS+. Thermogravimetric analysis showed that dietary fiber showed three stages of weightlessness before and after modification. The analysis of laser particle analyzer shows that the particle size of UIDF particles decreased and the distribution was more concentrated. SEM analysis showed that the surface of USDF becomes smooth， while the number of UIDF pits and wrinkled skirts increased. FTIR showed that the peak shape and fundamental position of characteristic absorption peaks of USDF and UIDF are not changed， but the intensity of some peaks was weakened. XRD analysis showed that ultrasonic diffraction diffraction did not caused a change in the crystal structure of SDF and IDF； GC-MS results showed that the dietary fiber of the sunflower meal were mainly composed of arabinose， rhamnose， xylose， mannose， galactose， and glucose.