The influence of GaN seed morphology on the growth of ZnO rods by solution-based process is investigated. The orientation, defect density, and crystallinity of ZnO rods are systematically studied in this research. The structural properties of ZnO rods are investigated using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). With different solution concentration treatments, the scale of ZnO rods is controlled with a wide size range from 130 nm up to 2.5 mu m in diameter. Our investigation demonstrates that the morphologies of GaN seeding layers have strong influences on the features of the ZnO rods grown thereon. The low-temperature heteroepitaxy of ZnO mirco/nanoarchitecture arrays on GaN can be very useful for many device applications, especially for light-emitting diodes.