TiO₂thin films were deposited onto glass plates by PECVD for the preparation of photocatalytic thin film. TTIIP was used as a precursor and mixed with oxygen and argon. Effects of deposition temperature, discharge power, deposition pressure and O₂/Ar gas flow ratio on the structure of the film and the photocatalytic performance were investigated. The TiO₂films showed the structural change from amorphous state to anatase crystalline state at 400℃. A film prepared at 400℃, 10W, gas flow ratio of 20sccm/100sccm, and 2.1×10^(-1)torr showed the best photocatalytic performance, which was evaluated based on the degradation efficiency of methylene blue under UV-A light. The photocatalytic performance depended more on the deposition temperature than the discharge power.