Well-aligned hexagonal ZnO nanotubes (NTs) arrays were synthesized on pretreated indium tin oxide (ITO) substrates by a simple hydrothermal method. The morphology and structure of the products were characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). A new method of substrate pretreatment was introduced to prepare ZnO coated films. The size of ZnO seeds and the formation rate of ZnO NTs were investigated. Further, the mechanism of the preparation of ZnO NTs was discussed. The photoluminescence (PL) spectrum measurement shows fairly internal defects existing in ZnO nanotubes. Well-aligned hexagonal ZnO nanotubes (NTs) arrays were synthesized on pre-annealed indium tin oxide (ITO) substrates by a simple hydrothermal method. The morphology and structure of the products were characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis A new method of substrate pretreatment was introduced to ZnO coated films. The size of ZnO seeds and the formation rate of ZnO NTs were investigated. Further, the mechanism of the preparation of ZnO NTs was discussed. The photoluminescence (PL) spectrum measurement shows fairly internal defects existing in ZnO nanotubes.