In this paper, CdS thin films well-known to window layer for solar cell were fabricated by means of vacuum evaporation method treated with different substrate heating. During film fabrication the substrates were heated at 50, 75 and $100^{circ}C$, respectively. The thin films were then annealed at $200^{circ}C$ in atmosphere, and the electrical and optical properties were investigated. By annealing, the hexagonal structure of films was changed into cubic structure. Their transmissivity was also increased and moved to longer wave band. It was shown that the film fabricated with the substrate heat-treated at $50^{circ}C$ had the lowest resistivity.