Lanthanum trivalent ions (La3+) doped titanium dioxide (TiO2) nanopowders in the range of 20-60 nm were prepared successfully by plasma spray in the self-developed plasma spray equipment. The photocatalytic activity of samples at different doping concentrations in photocatalytic degradation of methyl orange was discussed. The nanopowders prepared were characterized by transmission electron microscopy, X-ray diffraction, ultraviolet-visible spectra, photoluminescence (PL) and X-ray photoelectron spectroscopy. The results show that La3+ doping increased the photocatalytic activity of TiO2 greatly, the optimal doping concentration was 0.5 at%. The La3+ doping decreases the particle size and the distribution of particle sizes becomes more uniform. The doped powders were the mixture of anatase and rutile phase. The contents of anatase phase decreased firstly and then increased with an increase in the contents of La3+. The intrinsic absorption band of La3+ doped TiO2 nanopowders appears red shift from that of pure TiO2 nanopowders. The intensity of PL spectra increases and then decreases with increasing the content of La3+. The PL spectral intensity reaches its peak when the ratio of La3+/TiO2 is 0.2 at%. There are O, Ti, C and La elements in the prepared La3+ doped TiO2 nanopowders, La element still exists in trivalent and Ti element always exists in tetravalent. (C) 2008 Elsevier Inc. All rights reserved.