Abstarct: In this research, we studied the surface morphology, structural, optical, electrical and opto-electrical properties (photoconductivity effect) of copper oxide (CuO) nanostructure thin films prepared on glass and FTO substrates by chemical bath deposition method. For samples characterizations the field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), UV-Vis. spectroscopy, current-voltage (I-V) characterization were used. For preparation of CuO thin films, a mixed solution of copper (II) chloride dehydrate (CuCl2·2H2O), aqueous ammonia together with double distilled water were used. In this study the variable parameters are: the deposition time and annealing, time duration and annealing temperature (section 4.2), precursor concentration (section 4.3) and finally the kind of substrate (glass and FTO) (section 4.4). Depending on the growth conditions, the FESEM images of the samples indicated the formation of various nano-structures including nano-strings and nano grains on the surface of the laxyers. The X-ray diffraction patterns show the formation of monoclinic phase in the polycrystalline structure preferentially in (-111) direction for all samples and formation of additional phases including Cu2O and atacamite (Cu2Cl(OH)3) in annealed conditions and high concentration precursors, respectively. We also found that the annealing process can improve the electrical and opto-electrical properties (photoconduction effect) of the samples compared to as-grown ones.