Structural transformation of nanocrystalline titania prepared by sol-gel process with hydrolysis precursor titanium isopropoxide was investigated. The growth kinetics of TiO2 anatase was also studied. It is found that under acid conditions, the activation energies for the growth of anatase below and above 250℃ are (15.8±4.5) kJ/mol and (80.2±1.0) kJ/mol, respectively, which is due to the structural transformation from anatase to rutile resulting from the increasing temperature during the autoclave heating process. Under base conditions, the activation energy of anatase growth is (3.5±0.4) kJ/mol. The growth of anatase under acid conditions is slower than that under base conditions without phase transformation. That is, the growth of anatase becomes significant at higher temperature under acid conditions, whereas under base conditions, the crystallite growth is obviously accelerated by the longer autoclaving time. The above research results will contribute to realize the control of TiO2 nanoparticle size and will also provide us the theoretical and experimental bases for the mass production of TiO2nanoparticles in the future.