A series of leaching and electrochemical experiments were conducted to elucidate the critical role of hydrogen sulfide (H₂S) in copper-driven reduction of chalcopyrite. Results demonstrate that in the absence of H₂S, metallic copper converts chalcopyrite into bornite (Cu₅FeS₄). However, the introduction of H₂S promotes the formation of chalcocite (Cu₂S) by altering the oxidation pathway of copper. Electrochemical analysis demonstrates that the presence of H₂S significantly reduces the corrosion potential of copper from 0.251 to −0.223 V (vs SHE), reaching the threshold necessary for the formation of Cu₂S. Nevertheless, excessive H₂S triggers sulfate reduction via the reaction of 8Cu+H₂SO₄+3H₂S=4Cu₂S+4H₂O (ΔG=−519.429 kJ/mol at 50 °C), leading to inefficient copper utilization.