Zinc Oxide nanoparticles have been prepared by chemical precipitation method using Zinc nitrate. The effect of different parameters on particle size (growth temperature, concentration of (NaOH) and time of stirring) were studied. The prepared (ZnO) nanopowder was characterized by X-ray diffraction (XRD), Transmission Electron Microscope (TEM) and Fourier-transform Infrared Spectrometer (FT-IR). (XRD) patterns proved that (ZnO) nanoparticles had a hexagonal crystal structure and the particle size varied from (11.1-18.3) nm. (TEM) picture reveals the morphology and particle size of Zinc Oxide nanoparticles. The presence of defects and impurity contents in (ZnO) nanoparticles were  characterized by Fourier-transform infrared (FTIR) spectrometer.