ZnO nanorods are grown on Si-based substrate by chemical bath deposition method in aqueous solution using zinc nitrate hexahydrate. Various substrates having different surface morphology are used to evaluate their effect on growing ZnO nanorods, such as flat Si(100) wafer, small and large textured-Si wafer, porous silicon, flat SiO2 wafer, small and large textured-SiO2 wafer. The length, diameter, geometry, and coverage density of ZnO nanorods are investigated by field-emission scanning electron microscopy and summarized. SiO2 is a preferred substrate for the growth of ZnO nanorods to Si if the surface morphology of substrate is same, and the textured surface has much higher coverage density (> 95%) than the flat surface. Each nanorod is vertically grown along the c-axis on the top of each pyramid face for textured substrate, and forms the 3D sea sponge-like ZnO structure. The characteristics of ZnO nanorods grown on various substrates are analyzed by grazing-angle X-ray diffraction (XRD) and photoluminescence (PL) measurements.