A peculiar tower-like ZnO nanostructure was synthesized using an economical and facile hydrothermal method, with zinc acetate [ZAc, Zn(CH₃COO)₂ · 2H₂O] and hexamethylenetetramine (HMTA, C6H12N₄) as the source materials. The as-synthesized tower-like ZnO was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The characterization results indicated that the tower-like ZnO nanostructures are high-quality monocrystals. The as-synthesized ZnO nanostructures may have application in sensing area due to its high specific surface areas. The growth mechanism, as well as the optical properties of the as-synthesized tower-like ZnO nanostructures was also studied.