Abstract: Chemical composition of the surface layer formed at different potentials in collectorless flotation solution at pH 6.97 was studied by cyclic voltammetry and X-ray photoelectron spectroscopy. The sulfur element existed in the surface layer mainly in the metastable phase forms of CuFe(1-x)S2, CuS2, and the stable phase of S^n- at open-circuit potential(OCP). When the potential increased to 0.1V/SCE, S^n- disappeared while plentiful amounts of S⁰ and a small quantity of S2O3^2-/SO4^2- species were found in the film. At potentials higher than 0.35V/SCE, the content of S⁰ in the surface layer was lower than that in the surface layer at 0.1V, although the content of S2O3^2-/SO4^2- species increased dramatically. In addition, Cu element was present in the surface layer at lower potential in the form of CuFe1-xS2, and CuO present at higher potentials. Fe existed in the surface layer at lower potentials in the form of FeOOH and Fe2O3, and large amounts of Fe(OH)3 precipitated on the chalcopyrite surface at higher potentials.