Nb2O5 nanowires were synthesized by thermal oxidation process on Nb foils. The phase, morphology and microstructure of the products were characterized by using XRD, SEM and TEM. The optical absorption and photocatalytic dye degradation properties of the nanowires were also investigated. The results show that the sample is composed of pure Nb2O5 with tetragonal structure. The diameter of the nanowires is 20 to 60 nm. When the oxygen flow rate is 25 sccm, the nanowires with high aspect ratio are densely distributed into the network structure. The quantity and density of the nanowires are decreased when the oxygen flow rate is increased. The UV-Vis absorption spectrums show that the Nb2O5 nanowires are direct-band-gap semiconductor with the band gap of ~ 3.42 eV. Under the illumination of UV light with the wavelength of 365 nm, the nanowires exhibit obvious photocatalytic property to methylene blue, methyl orange and rhodamine B, for which the photocatalytic efficiency factor is -0.025, -0.021 and -0.008 min-1, respectively.