The ternary compound semiconductor CuInS2 is one of the most attractive materials for high efficiency solar cells due to its bandgap of 1.55 eV which is well matched to the solar spectrum. We deposit CuInS2 films on float glass substrates by a reactive RF sputter process using a Cu-In alloy target and H,S gas. By optimizing the sputter parameters, such as the sputter power, temperature of the substrate, and the flow of H2S. high quality films were obtained. The surface morphology, phase structure and composition of the layers were analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD). energy-dispersive X-ray analysis (EDX) and Rutherford backscattering spectroscopy (RBS), respectively. The electrical properties of the films were characterized by Hall effect measurements. photoluminescence (PL) and transmission measurements were performed to examine the optical properties of the films, and the absorption coefficients and the direct band gap of the films were evaluated by transmission measurements.