Abstract: Soybean protein isolate（SPI） was used as the research object, the effect of ultra-high pressure（0.1, 100,200, 300 MPa） on the structure of SPI and the antioxidant activity of its enzymatic hydrolysates during the simulated gastrointestinal digestion were analyzed. The results showed that the structure of SPI changed obviously after 200 MPa treatment. With the progress of digestion of the sample through the stomach and small intestine, the reducing ability, free radical scavenging ability and inhibition of liposome oxidation ability of digestive juice were improved. Compared with other treatment groups（0.1, 100, 300 MPa）, the maximum scavenging rates of DPPH radical and hydroxyl radical in the digestive juice of SPI hydrolysates treated with 200 MPa were 96.8% and 58.6%, respectively when digested for 4 hours, and the inhibition of liposome oxidation was the strongest at 5 h after digestion. The maximum reducing ability, scavenging rates of O₂^-· and ABTS radical were 0.462, 79.7% and 4.5% when digested for 10 hours. Comprehensive analysis showed that the pressure of 200 MPa could induce structural changes of SPI and improve the antioxidant activity of the digestive products from stomach and intestines. These results provided a theoretical basis for the application of high pressure processing enzymatic hydrolysates of soy protein isolate in the development of antioxidant food.