<p>Although numerous studies have investigated methods to improve the stability of egg yolk–based emulsions, comparatively fewer have focused on high–internal–phase emulsions such as mayonnaise. This study aims to enhance the thermal stability of mayonnaise by employing composite enzymatic hydrolysis, addressing common challenges such as oil–phase separation and structural collapse during thermal processing. A comparative analysis of phospholipase A₁ (PLA₁) and phospholipase A₂ (PLA₂) revealed that PLA₂ exhibited superior effectiveness in improving emulsifying activity (EA) and emulsion stability (ES). Notably, increasing PLA₂ concentration reduced both the contact angle and interfacial tension of the samples. To further refine the process, response surface methodology was applied to optimize the composite enzymatic digestion using PLA₂ and flavor protease (Fla). The optimal conditions were 2.3 U PLA₂, 92 U Fla, 55℃, and a reaction duration of 2&#xa0;h. The primary influencing factors were the addition amounts of PLA₂ and Fla. Under optimized conditions, the mayonnaise achieved a <i>L/l*</i> value of 25.523 ± 0.14, indicating significant improvement in thermal stability. Rheological and microstructural analyses revealed that the optimized samples exhibited no noticeable protein aggregation or oil droplet flocculation. This study provides a theoretical basis and practical, feasible solutions for industrial production and quality enhancement of mayonnaise, broadening its potential application across diverse food sectors.</p>