A microwave-assisted hydrothermal method was employed to synthesize nitrogen doped titania nanoparticles. Due to the high heating efficiency of microwave, rapid synthesis could be achieved in comparison with the conventional oven. Mixed crystal lattice was found existing in the obtained product, and the phase transformation behaviour under calcination was studied by XRD measurement together with Raman spectroscopy in details. The obtained nitrogen doped titania showed high specific surface area, about 300 m(2) g(-1). Photocatalytic activity in destructing NOx gas by the prepared sample exceeded that of commercial titania (P 25) or nitrogen doped titania synthesized by conventional hydrothermal method, under both visible-light and ultraviolet-light irradiation. (C) 2009 Elsevier B.V. All rights reserved.