ZnO nanorods co-doped with indium and gallium were grown on p-GaN films by low-temperature hydrothermal method. The results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS) show that indium and gallium have been dissolved in the ZnO lattice. Scanning electron microscope (SEM) observation shows that ZnO nanorods have good c-axis orientation. With increasing indium and gallium co-doping concentration, the diameter of the nanorods decreases and the density increases. XRD results show that the incorporation of indium and gallium causes the lattice constant of ZnO to increase, resulting in the (002) diffraction peak shifting to a low angle direction. At the same time, the optical properties of ZnO are affected by the co-doping of In and Ga. The UV emission peaks of co-doped ZnO nanorods all show a slight red shift, which is the result of the combined effects of surface resonance and band gap reforming. The I-V characteristics curves show that the n-ZnO nanorods/p-GaN heterojunction has better conductivity with increasing indium and gallium co-doping concentration.