Cu(OH) 2 nanowires were prepared rapidly by the precipitation method at room temperature, using CuCl 2 , K 2 CO 3 and NaOH as raw materials. Hierarchical copper oxide nanowires were obtained via a simple thermal conversion reaction of the Cu(OH) 2 nanowires at 300°C for 2h. The influence of reaction conditions on morphologies of the CuO products and the reaction mechanism were studied based on series of control experiments. The crystal structure and morphologies of the products were characterized and the optical properties of the CuO nanowires were investigated by UV–vis diffuse reflection absorption spectrum and fluorescence spectrum. The results show that the hierarchical CuO nanowire is about 10–15nm in diameter and 300–500nm in length with a primary particle size of 12.4nm. The usage of K 2 CO 3 and adequate NaOH is decisive for formation of the CuO nanowires. This preparation can be simply scaled up for a mass production.