The structure，optical and electrical properties of different Cl- concentrations doped CdS thin film deposited by electron beam evaporation using the mixture of CdS and CdCl2 has been investigated by means of X-ray diffraction (XRD), four probe tester and ultraviolet-visible spectroscopy. The results indicate that the films prepared by this method are polycrystalline structure with preferred growth orientation (002) which perpendicular to plinth, known as hexagonal phase, the crystallinity of the samples can be improved when the Cl- doping mole fraction is 0.1% and the influence on the optical energy gap is small，the variation is 0.07 eV. The minimum of the bright resistance is 100 Ω/□ and the photo sensitiveness reaches 2.9×105. In conclusion, the crystallinity, optical and electrical properties of CdS thin films can be improved after the Cl- doping process.