Rod-like and dentritic ZnO nanostructures were synthesized in a solution in the presence of PEG (200, 400, 600, and 1000) as the template at room temperature. The products were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and optical absorption measurements. The effect of reaction time, dosage and molecular weight of PEG on the morphology and size of ZnO was investigated in detail. The possible growth process of ZnO nanostructures under the assistance of PEG was discussed.