In this study, soy protein isolate (SPI) was treated by modified atmosphere packaging (MAP) assisted dielectric barrier discharge (DBD) cold plasma (CP) to improve its functional properties. For this reason, SPI powders were treated with DBD-CP at the oxygen ratio of 20 %, 30 %, 40 %, 50 % and 60 %, respectively. The results showed that with the increase of oxygen content, the structure of SPI was destroyed, protein macromolecule depolymerized. However, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirmed that the primary structure of SPI was not disrupted. In addition, when the oxygen content was greater than 40 %, the solubility, water holding capacity, gelling, emulsifying and foaming properties of SPI were significantly improved (p < 0.05). The results showed that high-oxygen packaging can increase the active particles generated during processing, thereby optimizing the structural and functional properties of SPI. Therefore, MAP can serve as a more efficient method for DBD-CP to modify soybean protein.