Titanium hydroxide obtained from the reaction between TiOCl2 and NH4OH solutions was aged in boiling water or HCl solution at 60 degreesC for 24h, then anatase or rutile-typed TiO2 nanocrystalline powder with a large specific surface area was synthesized. The influence of the aging conditions on the crystallization, microstructure and specific surface area of the prepared TiO2 powders was investigated, It was round that the powder aged in boiling water showed the anatase phase with spherical shape and the anatase or rutile powder with different particle shape was obtained by varying molar concentration of HCL The powder aged in HCl solution showed the largest specific surface area of 250 m(2)/g.