Sunflower seed protein is a protein rich in amino acids, but its structure is more difficult to be applied due to its poor functional properties. The purpose of this study is to investigate the effect of cold plasma treatment on the structural and functional properties of sunflower seed protein. The results showed that the energetic particles and active substances generated by cold plasma treatment could improve the spatial structure of the protein by bombardment/etching and oxidation, respectively, which led to the change of its secondary structure: α-helices and random coil were transformed to β-sheet and β-turns, and the tertiary structure: the fluorescence intensity was increased, the roughness was decreased, which finally led to the increase of the zeta-potential, the solubility increased to 7.341, and the emulsion increased to 7.341, which led to the increase of the solubility and the fluorescence intensity. to 7.341, and the emulsion activity index and emulsion stability index increased from 1.842 m2/g, 107.5 min to 3.3887 m2/g, 171.4 min. These changes were attributed to the fact that the cold plasma treatment altered the structure of sunflower proteins from tightly hydrophobic to loosely hydrophilic, with the exposure of the internal hydrophobic groups and the protein aggregation from large to small. This provides a theoretical basis for its application in food. Display omitted •Cold plasma treatment is a new modification method.•The mechanism of modification of sunflower seed protein by cold plasma was discussed.•The solubility of sunflower seed protein increased from 2.65 to 7.341.