In this paper CdO films of 3.8 μm thickness were deposited onto glass and Si-wafer substrates by spray pyrolysis technique at 250oC temperature. The structure, optical and electrical properties were investigated. The structure of the films were studied by X-ray diffraction have polycrystalline structure with (111) preferential orientation. The films have good transmittances in visible and NIRregion, with direct optical band gap (2.5eV).The electrical conductivity was measured as function of temperature and theactivation energy was about(0.155and 0.241) eV.The electrical characterization of CdO/Si hetrojunction diode was investigated by current –voltage studied.The reverse current strongly increased with illumination intensity and voltage bias.