KTa0.5Nb0.5O3 thin films were deposited on Si(0 0 1) substrates by pulsed laser deposition (PLD) with different oxygen pressures (10 Pa, 15 Pa, 20 Pa, 25 Pa and 30 Pa). The effect of oxygen atmosphere on the structure and refractive indices of the films were studied. It is found that the phase structure, the scale of the grains, the surface roughness and the optical properties of the films are sensitive to oxygen atmosphere variation. The refractive indices of the films were investigated by ellipsometer and the dispersive behavior was analyzed by Cauchy dispersion model. The films grown with 15 Pa oxygen pressure show the pure perovskite structure and the dispersion behaviors possess the normal dispersion shape; and other influence on the quality and properties of KTa0.5Nb0.5O3/Si(0 0 1) films were discussed. (C) 2011 Elsevier B.V. All rights reserved.