In the present work we synthesize nano powders of CuO by precipitation method, using CuCl2 as precursor. The obtained powder has undergone a heat treatment annealing 100°C, and 450°C. Structural analysis by X-Ray diffraction, Fourier transform infrared (FTIR) microscopy and scanning electron microscopy (SEM) reveal that CuO nano particles are in nano graphs forms and with improved crystallization at 450°C, annealing temperature as monoclinic crystal lattice structure. The radius of NCs calculated by the Scherrer formula is 12.31 nm