CdS thin films were deposited by simple and easy successive ionic layer adsorption and reaction (SILAR) method. Prepared thin film were annealed at 250°c in air for 30 minutes. The crystallographic structure and the crystallite size were studied by the X-ray diffraction (XRD) pattern and optical band gap were studied by optical absorption spectroscopy and electrical measurements by means of I-V measurement in dark and illumination condition, electrical resistivity studied by using two probe method.The crystallite sizes were found to increase, and it shows the hexagonal structure. The optical energy band gap observed to be decreased from 2.45 to 2.42 eV for as deposited and annealed film respectively. The electrical properties of these films were studied by I –V measurement in dark illumination (100W) condition. As the light intensity increases the photo current goes on increasing and the resistivity decreases. So film exhibits photoconductivity phenomena suggesting its useful for sensors and photovoltaic device and from thermoemf measurements, the electrical conductivity was found to be of n-type conductivity.