Abstract: TiO₂ nanopowders were synthesized via a simple, quick and sol-gel low-temperature combustion method. Their formation mechanism was explained from the chelating action of citrates. The effects of the molar ratio of metal ions to citric acid and the presence of impurity ions on the phase forming of TiO₂ nanoparticles and the crystallite size of the synthesized powders were investigated by thermal analyses (DTA/TG), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Spheric TiO₂ nanoparticles whose sizes are in the range of 40 to 90 nm are successfully prepared in the experiment. XRD results show that the mass fraction of rutile in the synthesized powers reaches 91% when the molar ratio of metal ions to citric acid is 0.5.