ZnO nanorods are fabricated by hydrothermal method on glass substrates that are covered with a ZnO seed layer by the thermal decomposition of zinc acetate. The influences of the thermal decomposition temperature on the structural and the optical properties of the obtained ZnO nanorods are carefully studied by using X-ray diffractometry, scanning electron microscopy and spectrophotometry. It is found that the crystalline quality, head-face dimension, macro stress, and transmissivity are found to be dependent on the thermal decomposition temperature. The 〈002〉c-axis-preferred orientation of the obtained ZnO nanorod is first enhanced and then weakened; the macro tensile stress first decreases and then increases; the average transmissivity first increases and then decreases as thermal decomposition temperature increases. When the thermal decomposition temperature reaches 350 ℃, the c-axis preferred orientation is strongest; the tensile stress is smallest; the average transmissivity in the visible region is maximal for the obtained ZnO nanorod. The surface scattering induced by the head-face dimension is the key mechanism of the average transmissivity of the obtained ZnO nanorod in the visible region.