Photo-catalytic nano titanium dioxide film has been prepared by electrochemical oxidation process. The microstructure and grain morphology in the film are characterized by TEM and XRD. The photo absorption character of the film is measured using spectrometer. It shows that porous amorphous titanium dioxide films are formed by the electrochemical oxidation process in the dielectric solution at an applied voltage and temperature. The amorphous film transforms into nano crystallized titanium dioxide film with anatase structure by means of heat treatment. The oxidation current density decrease with time increase at the voltage of 0~80 V in logarithm law. The grain size in the film is about 20 nm~40 nm. The film has high photo catalytic activity as demonstrated by the degradation test of acid red B in dye solution.