The global nanocrystalline anatase TiO2, particle can be obtained by hydrolysis of titanyl organic compounds. Its particle size is mostly influenced by the titanyl organic compounds' concentration, nitric acid (HNO3) concentration, reaction time and temperature, and especially the HNO3 concentration. The formation of nanocrystalline TiO2, with bigger size can be accelerated by a higher temperature, thick solution of reactant (titanyl organic compounds), and HNO3. Vice versa, in order to gain smaller particles, such as 6 nm, the reaction conditions should be set at a thin reactant solution, low temperature, and low HNO3 concentration. The reason lies in the hydrolyzing mechanism of titanyl organic compounds, which is strongly influenced by the temperature and pH.