Abstract：The development of composite films with both high electromagnetic interference (EMI) shielding efficiency (SE) and high mechanical properties still faces challenges. The design of multistage microscopic composite structures and multi-component cross-link enhancement strategies are possible to solve the above problems. In this study, carbon nanotubes (CNTs) and silver-coated nylon 6 (Ag@PA6) were successfully chemically anchored to poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers via vacuum filtration, chemical cross-linking, and ultraviolet cross-linking modification, and PVA/CNTs/PA6 composite films with multistage cross-linked reinforced structures were successfully prepared. Interestingly, PVA/CNTs/PA6 achieved highly efficient EMI SE at a lower dielectric filling, with the maximum loss of incident EM waves reaching 42.5 dB and EMI SSE/t reaching 11100.5 dB cm2 g−1. This particular multistage composite-enhanced network structure has satisfactory impedance/magnetic matching, dielectric loss, interface polarization, and internal multiple reflection scattering. In addition, the PVA/CNTs/PA6 films demonstrated excellent thermal management, infrared shielding, non-flammability, and mechanical properties. Notably, the internal crosslinking bond and interfacial hydrogen bond greatly improved the stability and mechanical property. This study has a practical application potential for the development of EMI shielding protection in flexible wearable electronic products.