Abstract: Ti nanoparticles were prepared by flow-levitation method. The morphologies,granularities, structure and properties of Ti nanoparticles were investigated by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The results show that the particles prepared by flow-levitation method are spherical and the average sizes gradually decreases with the increase of Ar flow rate. Under the flow rates of 0.6, 0.8 and 1.0 m³/h, Ti nanoparticles with the average sizes of 59, 50 and 41 nm are obtained. In the air, Ti nanoparticles mainly react with O.2 and form stable TiO₂. Meanwhile, Ti nanoparticles react with N₂ and vapor in the air, and a small amount of nitride and hydroxyl group were found.