In order to obtain low-frequency broadband absorbing materials, carbonyl iron/CoFe₂O₄/PANI ternary composites were prepared by co-precipitation and in-situ polymerization techniques. Using this as a dielectric layer, a metamaterial-based structure was designed based on the idea of metamaterials. The carbonyl iron composite absorbing coating improves the low frequency absorbing properties. The effects of the structural design of metamaterials on the absorbing properties of carbonyl iron/CoFe₂O₄/PANI coatings were analyzed, and the absorbing mechanism of the composite coatings with superstructures was studied and discussed. Through simulation optimization, it is found that when the resistance of the resistive film is 10mΩ/□ and the pattern size of the hollow cross-resistive film is optimal, the composite coating after giving the metamaterial structure at the same thickness has a wider width than the single carbonyl iron coating. The absorption band and the lower absorption frequency are less than -10 dB in the 3.8-6.9 GHz band. Studies have shown that the integration of metamaterial structure into the performance improvement of carbonyl iron coating can effectively improve its low frequency absorbing performance.