Composite thin films of PbTiO3 nano-crystals and high transparency PEK-c polymer were prepared by spin coating. The size of PbTiO3 nanocrystals was evaluated to be 30-40 nm. The transparency spectra of PEK-c composite thin film in 360-800 nm were measured. The optical constants n, k of the film in the wavelength range 400-620 nm were investigated by the transmission spectrum. The dispersion of refractive index fits well to a three-term Sellmeier relation. At 633 nm wavelength the refractive index of PbTiO3/PEK-c film was measured to be 1.6628 by a prism coupling method and showed a good agreement with the calculated value using the Sellmeier relation.