The photopolymerization of aromatic methacrylate in organic-inorganic nanocomposite films for holographic recording media was investigated. Thick photopolymer films (thickness>200 µm) were prepared using organic-inorganic hybrid solutions containing high refractive index monomers, through the sol-gel process. These photopolymer films were polymerized upon exposure to a visible light with high photo conversions. The photopolymerization was highly effective under visible light irradiation and could be applied to a holographic medium with high diffraction efficiency (>95 %) by using a 532nm laser. The diffraction efficiency of the film was much affected by morphology, which might affect monomer diffusion during the recording.