The immobilized photocatalyst, TiO2 film supported on activated carbon fibers （TiO2/ACFs） prepared with molecular adsorption-deposition （MAD）, exhibits high stability in cyclic photodegradation runs. The interposition fixing structure between TiO2 film and carbon fiber was investigated by means of SEM-EDX, XRD, XPS and FTIR, and a model was proposed to explain this structure. With SEM examination of carbon fiber surface after removing the deposited TiO2 film, a residual TiO2 super-thin film was found to exist still. By determining surface groups on ACFs, titanium sulfate （Ti2（SO4）3） in burnt remainders of the TiOE/ACFs was thought to be formed with an interracial reaction between TiO2 film and carbon fibers. These provide some evidence of finn attachment of TiO2 film to carbon fiber surface. In the consideration of characteristics of the MAD, the deposition mechanism of TiO2 film on ACFs was proposed, and the interposition fixing structure was inferred to intercrossedly form between TiO2 film and ACFs＇ surface. This structure leaded to firm attachment and high stability of the TiO2 film
