The phase and morphology transformation during the hydrothermal treating process of Y_2O_3 was evaluated with X-ray diffcrcnce (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size and specific surface area determination.The results showed that the cubic Y_2O_3 did not transfer into hexagonal Y(OH)_3 in pure water. Therefore, pure hexagonal Y(OH)_3 with nanotube and microrod morphologies were obtained by hydrothermal treating Y_2O_3 at 150℃ for 12 h in 15 ml of 2 mol/L NaOH solution with and with-out PVA or PEG It was suggested that the characteristic preferential growth of Y(OH)_3 was attributed to the structure anisotropy of hexahedron Y(OH)_3. The addition of PVA or PEG could promote the forming process of nanotubes by selective adsorption on different crystal planes,which altered the growth rate along different directions and resulted in the diffusion limit of constructing ions in the center top of rods. Finally,Y(OH)_3:Eu and Y_2O_3:Eu nanotubes were also synthesized by using this method, and their photoluminescence properties were evaluated.