In this paper, CdS thin films for the use of window layer in solar cell were fabricated by vacuum evaporation method to improve the reproducibility, The electrical and optical properties of thin films with the variations of substrates temperature and the variations of the film thickness were investigated. As increasing the substrates temperature the resistivities of films were increased. The samples transmissivity were shown over 70% when the wavelength were above 500 nm. In the films with 280 nm thickness, its transmissivity were reached 100%. The resistivities of the samples were decreased as increasing its thickness.