GaN has been widely used in the fabrication of ultraviolet photodetectors because of its outstanding properties. In this paper, we report a graphene–GaN nanorod heterostructure photodetector with fast photoresponse in the UV range. GaN nanorods were fabricated by a combination mode of dry etching and wet etching. Furthermore, a graphene–GaN nanorod heterostructure ultraviolet detector was fabricated and its photoelectric properties were measured. The device exhibits a fast photoresponse in the UV range. The rising time and falling time of the transient response were 13 and 8 ms, respectively. A high photovoltaic responsivity up to 13.9 A/W and external quantum efficiency up to 479% were realized at the UV range. The specific detectivity D^* = 1.44 × 10¹⁰ Jones was obtained at –1 V bias in ambient conditions. The spectral response was measured and the highest response was observed at the 360 nm band.