Abstract: As an effective technique to modify structure of protein with the active radical particles, cold plasma has been widely applied in modifying proteins to improve its functionality. The effects of dielectric barrier discharge (DBD) plasma treatment (20-120 s treatment time with 40 kV, 12 kHz) on the gelling properties of soy protein isolate (SPI) were investigated. Structural modification of SPI was determined using sodium dodecyl sulfate-polyacrylamide-gel electrophoresis (SDS-PAGE) and multi-spectroscopic analyses. The textural properties of the gels were determined by SEM, texture and dynamic rheological analyses. The results indicated that the SPI gel with 40 s plasma treatment displayed a compact sheet-like microstructure. Compared to untreated sample, it showed 2.63 and 5.98-fold increases in hardness and adhesiveness, which achieved excellent gel properties. A gradual weakening in gel properties was observed with prolonged treatment time (60-120 s). The results showed that the carbonyl content increased from the initial value of (2.39±0.09) μmol/g to (3.41±0.50) μmol/g with a mild oxidation induced by plasma treatment (40 s), and reached 4.36±0.16 μmol/g with an excessive oxidation induced by prolonged plasma treatment (120 s). The free sulfhydryl content gradually decreased from (4.49±0.13) μmol/g in untreated control samples to (3.86±0.09) μmol/g after exposure to plasma for 20 s, and further declined to (3.25±0.04) μmol/g after 40 s of plasma treatment. Further structure analyses in SPI showed that primary and secondary structures of glycinin were unaffected with plasma treatment. The underlying mechanism for enhancement of SPI gel ability was ascribed to the plasma-induced active radical particles, oxidated free sulfhydryl to sulfur radical, facilitating the generation of intermolecular disulfide bonds. However, excessive oxidation reduced the strength of SPI gel. Therefore, cold plasma, as a novel non-thermal processing technology, has great application prospects in protein structural modification to improve its functionality, but further research is required to control cold plasma processing parameters to avoid the adverse effects of excessive oxidation.