A new sol-gel method was introduced to prepare titanium oxides (TiO2) photocatalytic thin films using peroxide (H2O2) and titanyl sulfate (TiOSO4) as raw materials. The TiOSO4 solution was precipitated by adding ammonia solution, then peptized with 30% H2O2 solution to get a yellow, stable, neutral, and transparent liquid (peroxo titanic complex sol). When the peroxo titanic complex sol was autoclaved above 80℃ for 2h, it changed to a stable, semitransparent sol containing needle-like, ultra-fine anatase crystals less than 20nm in diameter. Titanium oxide (anatase) films used for photocatalysis can be prepared on substrates by a dip-coating technique using peroxo titanic complex and autoclaved sols.