Abstract: Titanium dioxide photocatalyst powders were prepared with the sol-emulsion-gel method. The influence factors, such as surfactant concentration, pH values of solution, water content and calcination temperature,
on the size and distribution of TiO₂ nanoparticles were investigated. The results show that TiO₂ nanoparticles are very small when the concentration of the surfactant reaches the critical concentration
of 9.20×10^-4 mol/L and a good distribution can be obtained. Nucleophilic reaction will occur in the basic solution for the Ti(OC₄H₉)₄, the TiO₂ nanoparticles with the smallest size will
be obtained when the pH value is 8.4. The size of TiO₂ nanoparticles will decrease rapidly with the increasing of water and it will reach a steady constant when the water content is 0.5mol/L. The crystallinity
of TiO₂ nanoparticles can be improved by calcination, which makes the amorphous phase transform to anatase and rutile. The shape of the particles can be noticed as:
Formed sphere→Rod→Sphere→Distorted sphere.

Key words: sol-emulsion-gel, nano-TiO2 photocatalyst, preparation, influence factor