Polycarbonate (PC)/Polystyrene (PS) double layer films have been irradiated with 55 MeV Carbon (C⁵⁺) ion beam at different fluence 1×10¹¹ to 1×10¹³ ions/cm². The XRD pattern show the decrease in crystallinity and increase average intermolecular spacing with the increase of fluence due to formation of nanoclustrues in polymer matrix. UV-VIS spectra show that the indirect and direct band gap was found to be decreases after irradiation and is depends on the ion fluence and growth of nanoclusters. The refractive index of PC/PS double layer films is decreases with fluence of irradiation. The FTIR spectra show that at high fluence the some bonds has cross linking and chain scissoring.