Ti ions were implanted into ZnS films at a dose of 1×1017ions/cm2 and energy of 80 keV by vacuum evaporation. After ion implantation， the as-implanted sample was annealed in argon ambient at different temperatures from 500 ℃ to 700 ℃. The effects of ion implantation and post-thermal annealing on the structural and optical properties of ZnS films were investigated by x-ray diffraction （XRD）， photoluminescence （PL） and optical absorption. The results showed that the diffraction peak intensity was recovered by annealing at 500 ℃. The optical absorption in the visible region increased after Ti ion implantation and the absorption edge blueshifted with the increasing annealing temperature. The PL emission intensity increased with the increasing annealing temperature.