Abstract: In view of the demand for electromagnetic protection of military electronic equipment in modern electronic warfare, electromagnetic shielding flexible composites were prepared by copper plating technology and multilayer gradient structure design with carbon fiber mats as the substrate. The parameters (carbon fiber mat area weight, composite gradient structure and magnetic filler addition) affecting the on the electromagnetic shielding performance were investigated and the shielding mechanism was studied. The results show that the electromagnetic shielding performance of the composites gradually increases with the increase of the area weight of carbon fiber mats. On this basis, the constructed multi interface and gradient structure can effectively improve the shielding performance up to 52 dB (8-12 GHz). Further, by adding 50 wt.% iron tetraoxide nanoparticles (Fe₃O₄ NPs) to the thermoplastic polyurethane matrix (TPU), the shielding effectiveness can reach up to 67 dB (8-12 GHz). Thanks to the multilayer gradient structure design and the synergistic effect of electromagnetic functional materials, the composites demonstrate excellent shielding performance and good flexibility with a thickness of only 1 mm, which can meet the demand for shielding and protection materials for portable military applications.