Heteropolyacid-imbedded polymer film catalysts were applied for the vapor-phase catalytic reaction. Thin film catalysts were prepared by membrane technology using homogeneous heteropolyacid-polymer solutions. It was found that heteropolyacid was finely and uniformly dispersed throughout the polymer matrix. Heteropolyacid catalyst could be designed by this method to enhance acid or oxidation catalysis. Future aspects of the film catalyst were also described in this work.