In recent years, the utilization of copper tailing and removal of sulfur dioxide (SO2) have become the focus of research. In this study, copper tailing was used as an iron ion donator to remove SO2 from flue gas. To improve the desulfurization performance, the additive was selected from metal sulfates, such as ferrous sulfate, ferric sulfate, manganese sulfate, and scrap iron. A series of experiments were conducted in a bubble reactor to study the effects of various critical factors, including the inlet SO2 concentration, solid/liquid ratio, dosage of additive, gas flow rate, O-2 concentration, and reaction temperature, on the flue gas desulfurization performance. Various characterizations, such as X-ray fluorescence spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy with energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma spectroscopy, and titration, were used to study the properties of copper tailing and absorption liquid. Furthermore, the reaction mechanism of SO2 removal was also studied. The results showed that copper tailing combined with MnSO4 center dot H2O exhibited the highest SO2 removal efficiency. The desulfurization efficiency reached approximately 99% and was mainly affected by the flue gas flow rate and the absorption temperature. Mn2+ served as a catalyst for liquid-phase catalytic oxidation. Furthermore, the leaching reaction contributed to the consumption of some H+, whereas Fe2+ (primarily leached from fayalite in the copper tailing) served as its activation state and variable valence state with Mn2+ for the efficient removal of SO2. Moreover, the reduction of flue gas desulfurization is attributed to the accumulation of SO42- and H+ in the slurry.