Well aligned ZnO nanorod arrays on Si substrate previously coated with a thin buffer layer of ZnO seeds via radio-frequency magnetron sputtering, which were synthesized by the aqueous solution method. The sample was characterized by scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy and selected area electron diffraction. The results show that ZnO nanorods have good crystal quality， are highly oriented and grown along c-axis. The full width at half maximum of the (0002) peaks of the nanorod arrays is only 0.06°. Furthermore, a strong and narrow eigen peak centered at 378nm and very weak emission in visible region due to impurities or defects were observed in the photoluminescence spectra.