Abstarct: In this thesis, first zinc oxide (ZnO) thin films, nanorods and nanoparticles were grown by sol-gel route. The average thickness of the films, diameter of the nanorads and size of the nanoparticles were 200, 160 and 150 nm, respectively. Then the effect of chemical parameters (such as pH value, type of solvent and stabilizer), physical parameters (such as drying and annealing temperature, aging of the sol) and Al doping on the structural, optical and electrical properties of the samples have been studied. X-ray diffraction spectra and FESEM images were used for structural characterization of the samples. Optical and electrical properties of the samples were investigated by the transmittance spectra, Hall and four probe measurements. XRD results showed that all samples were polycrystalline. Preferential orientation of the ZnO films and nanorods were [002], while for ZnO nanoprticles it was [101]. The optical transmittance measurements of the films showed a transmission of 80% in the visible range. It also showed that as-grown film has higher transmittance than the others. FESEM images of the Zno films, nanorods and nanoparticles showed a Y-shaped pattern with diameter of 500 nm, presence of hexagonal rods with diameter of 200 nm and lengths of about 1 micrometer, and some particles with average size of about 150 nm. Mobility and carrier concentration of the Al-doped sample were also investigated.