Abstract: To investigate the mechanism by which solid-state fermentation with Bacillus subtilis reduces the antigenicity of peanut protein, indirect competitive ELISA was employed to determine protein antigenicity, the ninhydrin colorimetric method was used to measure protein hydrolysis, and SDS-PAGE was utilized to assess protein molecular weight. Infrared spectrum, ultraviolet spectrum and endogenous fluorescence spectrum were applied to analyze the effects of structural changes in peanut protein on its antigenicity. Exogenous fluorescence spectroscopy was applied to analyze the surface hydrophobicity of peanut protein. The results demonstrated that solid-state fermentation with Bacillus subtilis significantly hydrolyzed peanut protein, resulting in a 67.6% reduction in antigenicity and a 55.03% decrease in the antigenicity of the major allergen Ara h 3 in peanut protein. After 72 hours of fermentation, the protein hydrolysis degree of peanut protein reached 9.40%. Major allergens in peanut protein are degraded, and the protein content with a molecular weight less than 15 kDa increased significantly. After fermentation, changes were observed in the relative content of secondary structure of peanut protein, with the relative contents of α-helix and β-turn decreased by 5.52% and 8.17%, respectively. The surface hydrophobicity of peanut protein gradually increased before 48 hours of fermentation, and after 48 hours of fermentation, the surface hydrophobicity of peanut protein gradually decreased with the fermentation time. In the early stage of fermentation, the tertiary structure of peanut protein changed, and the spatial structure gradually unfolded. But after 48 hours of fermentation, the microbial enzymatic hydrolysis weakened, accompanied by partial protein aggregation. Solid-state fermentation with Bacillus subtilis can disrupt antigenic epitopes by altering the structure of peanut protein, thereby reducing its antigenicity.