Abstract: In order to enhance the antioxidant effect of peptides in oil-based emulsion foods and reduce the use of additives, this study investigated the synergistic effect of hazelnut protein hydrolysates and vitamin E in delaying the oxidation of linoleic acid emulsions. Hazelnut protein hydrolysates were firstly prepared by alkaline protease hydrolysis with different hydrolysis times. Subsequently, the ability to scavenge ABTS⁺ free radical, reduce Fe³⁺, and delay oxidation of linoleic acid emulsion was evaluated. The combination index (CI) was used to assess the synergistic effect of hazelnut protein hydrolysates and vitamin E in delaying the oxidation of linoleic acid emulsions, with the aim of identifying the optimal ratio. The results indicated that both hazelnut protein and its hydrolysates exhibited significant free radical scavenging activity and reducing power. Within the tested concentration range, hazelnut protein demonstrated the highest free radical scavenging activity (21.28%±0.46%) and Fe³⁺ reducing power (0.11±0.01). Among the hydrolysates, the 8-hour hydrolysate showed the highest free radical scavenging activity (82.32%±0.47%), while the 6-hour hydrolysate exhibited the greatest Fe³⁺ reducing power (0.18±0.01). Furthermore, a positive correlation was observed between sample concentration and the ability to inhibit the oxidation of linoleic acid emulsions, and the hydrolysates demonstrated strong antioxidant activity at microgram concentrations, outperforming that of unhydrolyzed protein. Further studies demonstrated that the combination of enzymatic peptides and vitamin E significantly enhanced the inhibition of linoleic acid oxidation. Notably, the combination of 2-hour enzymatic peptides and vitamin E, at the final concentration of 100+10 μg/mL, expressed the most pronounced synergistic effect, with the inhibition rate of 81.97%±0.01% and a CI value of 0.02. Additionally, the combination of its 3~10 kDa fraction with vitamin E, at a final concentration of 200+2 μg/mL, also demonstrated prominent synergistic effect, with the inhibition rate of 72.44%±1.02% and the CI value of 0.22. These findings highlighted the potential of achieving "low addition, high efficiency" in emulsion food preservation through the combined utilization of protein enzymatic peptides and vitamin E. This study not only offers scientific insights into emulsion food preservation, but also emphasizes the potential value of hazelnut processing by-products.