The surface properties of sphalerite (ZnS) were theoretically investigated using first principle calculations based on the density functional theory (DFT). DFT results indicate that both the (110) and the (220) surfaces of sphalerite undergo surface atom relaxation after geometry optimization, which results in a considerable distortion of the surface region. In the normal direction, i.e., perpendicular to the surface, S atoms in the first surface layer move outward from the bulk (d_1 ), whereas Zn atoms move toward the bulk (d_2 ), forming an S-enriched surface. The values of these displacements are 0.003 nm for d 1 and 0.021 nm for d_2 on the (110) surface, and 0.002 nm for d 1 and 0.011 nm for d 2 on the (220) surface. Such a relaxation process is visually interpreted through the qualitative analysis of molecular mechanics. X-ray photoelectron spectroscopic (XPS) analysis provides the evidence for the S-enriched surface. A polysulphide (S~(2-)_n ) surface layer with a binding energy of 163.21 eV is formed on the surface of sphalerite after its grinding under ambient atmosphere. This S-enriched surface and the S 2 n surface layer have important influence on the flotation properties of sphalerite. The surface properties of sphalerite (ZnS) were theoretically investigated using first principle calculations based on the density functional theory (DFT). DFT results of that both the (110) and (220) surfaces of sphalerite subjected surface atom relaxation after geometry optimization, which results in a distortion distortion of the surface region. ie, perpendicular to the surface, S atoms in the first surface layer move outward from the bulk (d_1), while Zn atoms move toward the bulk (d_2), forming an S-enriched surface. The values ​​of these displacements are 0.003 nm for d 1 and 0.021 nm for d_2 on the (110) surface, and 0.002 nm for d 1 and 0.011 nm for d 2 on the (220) surface. A relaxation process is visually interpreted through the qualitative analysis of molecular mechanics. X-ray photoelectron spectroscopic (XPS) analysis provides the evidence for the S-enriched surface. A polysulphide (S ~ (2 -) _ n)of 163.21 eV is formed on the surface of sphalerite after its grinding under ambient atmosphere. This S-enriched surface and the S2 n surface layer have important influence on the flotation properties of sphalerite.