Pure perovskite phase and crack-free KTa0.5Nb0.5O3 thin films were prepared on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. The structure and orientation were analyzed by X-ray diffraction. The optical properties were investigated by an ellipsometer. The relationship between the refractive index dispersive behavior and internal structure was analyzed by Sellmeier dispersion model and single electronic oscillator approximation. The parameters of room temperature monomial Sellmeier oscillator were calculated. And the refractive index dispersive parameter E-0/S-0 of KTa0.5Nb0.5O3 thin films on Pt/Ti/SiO2/Si substrates is (6.72 +/- 0.04) x 10(-14) eVm(2), which is consistent with those of KTN crystals and compounds with ABO(3) perovskite type structure. (C) 2011 Elsevier B.V. All rights reserved.