Abstract: To crush the insoluble dietary fiber of soybean skin through pneumatic cracker with three different frequency which was 150, 250, 300 Hz, three different particle size of superfine dietary fiber DF-A, DF-B, DF-C were obtained, and the physico-chemical properties of them were compared. The median diameter of DF-C was 16.58μm, decreasing 2.5 times than DF-A. While the specific surface area had a trend of increasing with the particle size decreasing, the most specific surface area was 152.2m2·kg-1. The whiteness of DF-A, DF- B, DF-C were respectively 51.7%, 55.1%, 63.4%. Through the result of Duncan, the water-holding capacity of sample DF-A and DF- B had no significant difference (p>0.05) , the oil-holding capacity of DF-A, DF-B, DFC had significant difference (p<0.05) , the water-holding capacity of DF-A, DF-B, DF-C had significant difference (p<0.05) . The cation exchange capacity got strong gradually, until the consuming of NaOH was0.7mL. When the solution concentration was below 10%, the viscosity curve of them was steep, the viscosity number had rise trend. While the results of scanning electron microscope showed that the microstructure did not change with the decrease of the dietary fiber particle sizes, it still had a rod-shaped structure. Results showed that Jet mill increased the hygiene function of insoluble dietary fiber of soybean skin.