<p>The recycling of waste polymers plays a critical role in environmental sustainability. Recycled Ethylene Vinyl Acetate composites have attracted growing research interest. In this study, Recycled Ethylene Vinyl Acetate was used as the matrix and fly ash as the filler to investigate the effects of varying fly ash content on the mechanical properties, microstructure, and interfacial compatibility of Recycled Ethylene Vinyl Acetate composites. The results showed that an appropriate amount of fly ash significantly enhanced the tensile and flexural strengths of the composites. Notably, when the fly ash content reached 20 parts (REVA/AC/20FA), the tensile and flexural strengths increased by 15.62% and 27.2%, respectively, compared to pure Recycled Ethylene Vinyl Acetate. Overall, fly ash-reinforced Recycled Ethylene Vinyl Acetate composites exhibit potential application value for mechanical property enhancement, providing a theoretical and practical foundation for the development of cost-effective engineering materials. Future work should focus on optimizing surface modifications and filler content to further improve composite performance. Moreover, due to their improved mechanical strength, thermal stability, and cost-efficiency, these composites are promising candidates for use as intermediate core layers in aluminum composite panels (ACP), where vibration damping, thermal insulation, and sustainability are critical in modern construction.</p>