Abstract: Protein-polysaccharide complexes exhibit promising functionality as encapsulation wall materials to enhance the stability and bioavailability of bioactive components during delivery. In this work, zein-peach gum polysaccharide (PGP) nanocomposite particles were fabricated via antisolvent precipitation. The interaction mechanisms and structural organization of Zein-PGP composite nanoparticles were systematically investigated using multi-technique characterization, while their antioxidant capacity and colloidal stability were concurrently evaluated. The results showed that the primary forces driving the formation of nanoparticles between Zein and PGP were hydrogen bonding and hydrophobic interactions, which contributed to the stability of the composites. At the meanwhile, the incorporation of PGP significantly enhanced the radical scavenging capacity of the complexes. When the mass ratio of Zein to PGP was 1:1, the composite particles exhibited optimal stability, with a particle size of 156.73±5.17 nm, a PDI of 0.15±0.01, and a Zeta potential of −31.43±0.44 mV. The contents of α-helix, β-sheet, and β-turn in the composites were 45%, 12%, and 15%, respectively. Additionally, the presence of PGP enhanced the quenching of zein’s intrinsic fluorescence. These findings not only provide a new perspective for the combined utilization of zein and PGP but also lay a foundation for future applications of composite nanoparticles in delivering bioactive components in food industry.