Abstract: Non-stoichiometric carbides have been proven to be effective electromagnetic wave (EMW) absorbing materials. In this study, phase and morphology of XZnC (X = Fe/Co/Cu) loaded on a three dimensional (3D) network structure melamine sponge (MS) carbon composites were investigated through vacuum filtration followed by calcination. The FeZnC/CoZnC/CuZnC with carbon nanotubes (CNTs) were uniformly dispersed on the surface of melamine sponge carbon skeleton and Co-containing sample exhibits the highest CNTs concentration. The minimum reflection loss (RL_min) of the CoZnC/MS composite (m_composite : m_paraffin = 1:1, m represents mass) reached −33.60 dB, and the effective absorption bandwidth (EAB) reached 9.60 GHz. The outstanding electromagnetic wave absorption (EMWA) properties of the CoZnC/MS composite can be attributed to its unique hollow structure, which leads to multiple reflections and scattering. The formed conductive network improves dielectric and conductive loss. The incorporation of Co enhances the magnetic loss capability and optimizes interfacial polarization and dipole polarization. By simultaneously improving dielectric and magnetic losses, excellent impedance matching performance is achieved. The clarification of element replacement in XZnC/MS composites provides an efficient design perspective for high-performance non-stoichiometric carbide EMW absorbers.