Abstract: Nano titanium dioxide particles were synthesized by drolysis of TiCl₄,and the system is neutralized by Na₂CO₃ through the phase thransfer.At the same time,the particles were characterized by means of Transmission Electronic Microscope(TEM) and X-Ray Diffraction(XRD).The results showed that when the temperature is 55℃,the TiCl₄ solution was thransformed from n-octyl alcohol to deionized water phase and reacted with the deionized water,the precursors of nano-TiO₂-Ti(OH)₄ was dried for 6 hours in vacuum at 70℃,then calcined 3 hours in muffle furnace at 400℃.At last,the nano-TiO₂ which is uniform distribution,weak agglomeration was synthesized.The mechanism of both TiCl₄ hydrolysis reaction and phase-transfer reaction showed that temperature increase and pH of reaction system is in alkaline conditions by Na₂CO₃ solution neutralized H⁺ conducive to hydrolysis reaction to the positive movement.