Thin film photocatalysts of TiO2 coated glass tile were prepared to eliminate air pollutants, using the precipitation dropping method under various hydrolysis conditions. The surface structure of TiO2 films was changed, when changing the pH, the addition rate of NH4HCO3 and TiCl4 concentration. About 10 nm anatase TiO2 particles in sol solution were formed, when pH of the solution is 6, the addition rate of NH4HCO3 1.0 ml/min and TiCl4 concentration 0.03 mol/l. The morphology and the crystal structure of TiO2 film affect most. The photocatalytic decomposition of acetic acid was affected by both the morphology and the crystallinity of precipitated TiO2 particles.