ZnO-based nanomaterials can be used as sensors for different applications, including gas and ultraviolet (UV) ray sensors. To grow ZnO nanowires by the hydrothermal method, a ZnO seed layer was prepared by a sputtering method to deposit ZnO films on SiO2/Si substrates of about 200 nm thickness. Next, Zn(NO3)2‧6H2O and C6H12N4 were used as reagents, and DI water was used as a solvent, and they were mixed to the designed compositions. We found that when Zn(NO3)2‧6H2O and C6H12N4 were used as reagents to grow ZnO nanostructured materials, growth temperature, the concentration of the diluted solution, growth time, and the position of the substrates were four important factors affecting the synthesis results. The surface morphologies of ZnO nanowires were observed by field-emission scanning electron microscopy (FESEM), and crystalline phases were analyzed using X-ray diffraction (XRD) patterns. The FESEM images and XRD patterns were used to determine the effects of synthesis parameters on the morphologies and crystalline properties of the grown nanostructured materials. First, we found that 100 ℃ was the optimum synthesis temperature for growing pure ZnO nanowires, because ZnO-based nanowires could be successfully synthesized at different concentrations of Zn(NO3)2‧6H2O and C6H12N4 and different synthesis times. The effects of growth time, the position of the substrates on the carry sheet glass, and concentrations of Zn(NO3)2‧6H2O and C6H12N4 on the growth of nanostructured materials were also investigated.