NaNbO3 had been successfully developed as a new photocatalyst for CO2 reduction. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible spectroscopy (UV-Vis). The DFT calculations revealed that the top of VB consisted of the hybridized O 2p orbital, while the bottom of CB was constructed by Nb 3d orbital, respectively. In addition, the photocatalytic activities of the NaNbO3 samples for reduction of CO2 into methanol under UV light irradiation were investigated systematically. Compared with the bulk NaNbO3 prepared by a solid state reaction method, the present NaNbO3 nanowires exhibited a much higher photocatalytic activity for CH4 production. This is the first example that CO2 conversion into CH4 proceeded on the semiconductor nanowire photocatalyst.