Abstract: In order to determine the suitable steam explosion pressure parameters in the modification process of dietary fiber of old stem in broccoli,the steam explosion pressure 0.5,1.0,1.5,1.8 and 2.0 MPa were selected to study the effect on quality,physical and chemical properties of the dietary fiber of old stem in broccoli. The results showed that the powder with 0.5 MPa treatment had the best color and the largest expansion force(3.56 mL/g),while the oil holding capacity was the smallest. The soluble dietary fiber content of the powder treated with 1.0 MPa was the highest,reaching 8.89%,and the bulk density was bigges(0.337 g/mL). The specific surface area of the powder treated by 1.5 MPa was the largest,while the soluble dietary fiber content and water holding capacity were the smallest. The DPPH free radical scavenging ability of the powder treated by 1.8 MPa was the strongest,reaching 95.89%,which was 2 times of the control. The bulk density,oil holding power and nitrite adsorption capacity of the powder treated by 2.0 MPa were the largest,while the color was the worst. The powder treated by 0.5,1.5 and 1.8 MPa was suitable as a functional ingredient to be added to food or adsorbed on the surface of food. The powder treated by 1.0 MPa was suitable for capsules and other products,and the powder treated by 2.0 MPa was more favorable for tablets.