Abstract Ultrasonic spray pyrolysis method was used to prepare Nb-doped TiO 2 porous microspheres with an average diameter of 500 nm for solar photocatalytic applications. The effect of Nb-doping on morphology, structure, surface area, as well as spectral absorption properties of TiO 2 microspheres was investigated with SEM, TEM, XRD, Raman spectra, BET, and UV–Vis absorption spectra. The Nb-doping decreased the grain size of TiO 2 porous microsphere, and influenced its surface area and pore size distribution dependent on the doping concentration, but changed negligibly the morphology and size of TiO 2 microspheres. Moreover, the Nb-doping was observed to extend the spectral absorption of TiO 2 into visible spectrum, and the absorption onset was red-shifted for about 88 nm at a doping level of 5% compared to pristine TiO 2 microspheres. Under solar or visible irradiation, Nb-doped TiO 2 microspheres showed higher photocatalytic activity for methylene blue degradation compared with TiO 2 microspheres, which could be ascribed to the extended light absorption range and the suppression of electron-hole pair recombination.