Abstract: Sulfides are widely used and crucial microwave absorbers, but the strong reducing nature of S^2- renders Co₉S₈ and CuS susceptible to oxidation in the presence of oxygen, moisture, or high temperatures, leading to structural degradation and instability in their dielectric and magnetic properties. Herein, we prepared core-shell structured Co_1-xS@C and Cu₂S@C composites under high temperatures by coated carbon layers on their surfaces. The incorporation of a carbon layer not only enhances the chemical stability of the sulfide phase but also enables modulation of the carbon layer’s electromagnetic parameters through controlled pyrolysis. This tunability facilitates improved impedance matching and consequently broadens the effective absorption bandwidth (EAB) of the Co₉S₈ and CuS microwave absorbers. The as-prepared Co_1-xS@C and Cu₂S@C composites exhibit a minimum reflection loss (RL_min) of -43.42 dB at 2.7 mm and -44.12 dB at 3.0 mm, respectively, while Co_1-xS@C demonstrates an EAB of 5.01 GHz at 2.1 mm. Compared with Co₉S₈ (-1.02 V) and CuS (-0.80 V), the corrosion potential of the carbon layers encapsulated by Co_1-xS@C (-0.6 V) and Cu₂S@C (-0.54 V) is significantly higher than that of the structures without carbon layer encapsulation, demonstrating better chemical stability and corrosion resistance. The introduction of the carbon layer as a heterogeneous interface simultaneously enhances the interface polarization loss. The use of the dopamine polymerization method provides a means to design broadband microwave absorption materials.