Various ZnO nano and microstructures, such as nanorods, microflowers composed of nanorods, and microrods were hydrothermally self-assembled. The morphology of the formed ZnO nano and microstructures could be easily tuned by varying the experimental parameters of the NaOH concentration. The crystal structure of samples was investigated by XRD, and the diffraction peaks were indexed to hexagonal wurtzite structure. A possible growth mechanism was proposed on the basis of the morphology evolution of nano and microstructures observed by SEM. Furthermore, the photoluminescence and photocatalytic properties of ZnO nano and microstructures were investigated. The results show that the ZnO microrods and microflowers exhibited higher photodegradation efficiency than that of ZnO nanorods, which maybe due to the exposed polar faces of better crystalline rather than the size of ZnO.