Abstract: The impact of Fe³⁺ on chalcopyrite's surface properties and floatability is systematically studied.Many methods are hired, such as the flotation test, Zata potential test, ORP potential test, chemical analysis of Fe³⁺ solution, and X-ray photoelectron spectroscopy (XPS).The results show that with STG as an inhibitor, the recovery rate of chalcopyrite is reduced significantly by adding Fe³⁺ when the pH is in the range of 4-6.The Zeta potential of chalcopyrite increased significantly after Fe³⁺ treatment, but the ORP potential did not change significantly.Fe³⁺ in solution mainly exists in the form of hydroxy-complex iron ions, iron hydroxide precipitation, and a small number of iron ions.The physical and chemical adsorption of Fe³⁺ hydrolyzed derivatives on the chalcopyrite surface is the main reason for the decline of chalcopyrite flotation recovery.