In this research project, the surface of copper (II) oxide nanoparticles (CuO ) was modified by biosafe molecules contaning citric acid (CA) and ascorbic acid (AA). The prepared modified CuO (CuO-CA-AA) were investigated by different methods such as FT-IR, XRD, FE-SEM, TEM and TGA techniques. The FT-IR analysis confirmed grafting of CA and AA on the surface of CuO . The Morphology observations (TEM analysis) showed the reduction of average particle size of CuO after surface modification. Also, the surface modification of CuO nanoparticles were proved using thermal analysis. In the first project, series of poly(vinyl chloride) (PVC) nanocomposites (NCs) containing 4, 8 and 12 wt% of the CA and AA modified CuO nanoparticles were prepared (modification was performed using ultrasonic technique). The resulting NCs were characterized by different analyses such as FT-IR, XRD, TGA, UV-Vis, Mechanical testing, FE-SEM and TEM. According to the histogram diagrams and curvature of normal distribution obtained from TEM images, a very good dispersion of modified NCs in the PVC polymer matrix were observed. In the second project, poly(vinyl alcohol) (PVA) and 4, 8 and 12 wt% of CA and AA modified CuO nanoparticles were used as substrate and filler, respectively, in order to prepare the nanocomposites. All of the processes were performed under ultrasonic irradiation as a rapid and environmentally friendly method. The FT-IR, XRD, TGA, UV-Vis, Mechanical testing, FE-SEM and TEM were used to investigate the characteristics of the prepared nanocomposites. The termal stability and UV absorption of the NCs were enhanced compared to the pure polymer after addition of modified to the PVA substrate.