A new photocatalyst, TiO2 powder immobilized on polystyrene (PS) thin films, was prepared using a novelmethod and its photocatalytic activity on the photodegradation of acridine dye in aqueous solution was tested. By thismethod, the crystal form and grain size of the immobilized TiO2 were well maintained. Compared with TiO2 powder, thephotocatalytic activity of TiO2/PS thin films was not significantly reduced. The catalyst is stable and can be reused severaltimes without the loss of activity, which makes wastewater treatment using this photocatalytic degradation technique of thisway possible in the practical application.