TiO₂ is a wide band gap semiconductor with important applications in photovoltaic cells and photocatalysis. In this paper, single-crystalline rutileTiO₂ nanorod arrays were fabricated on the GaN based light emitting diodes (LEDs) with a TiO₂ seed layer by an acid hydrothermal process. The morphologies and the crystallinity of the rutileTiO₂ nanorod arrays on GaN wafer were characterized by scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction. The optical properties of surface-textured TiO₂/GaN were measured and analyzed by photoluminescence. The influence and dependence of the TiO₂ nanorod array with the different densities and diameters on the light output of the fabricated GaN wafers were investigated. The light extraction efficiency of GaN LEDs was enhanced by the single-crystalline rutileTiO₂ nanorod array, which showed an eight-fold increase in photoluminescence intensity compared to the normal planar surface. The mechanisms for the enhanced light output of GaN LEDs by the single-crystalline rutileTiO₂ nanorod arrays were discussed.