Titanate nanotubes (TNTs) were prepared by treatment of anatase-TiO2 nanoparticles in mild hydrothermal conditions. TNTs were characterized by XRD, TEM, FT-IR and BET specific surface area technique. It was found that nanotubes might be NaxH2-xTi3O7 and were formed during the hydrothermal process, rather than during the treatment process with acid solution. The formation mechanism of TNTs can be explained as 3D→2D→1D. After hydrothermally reacting at 130°C for 48h, the as-prepared products exhibit hollow nanotubes with open ends, more than 100 nm in length, 10 nm in outer diameters, large BET surface area and pore volume, which may lead to potential photocatalysis and absorption application.