In-depth compositional analysis of zirconium dioxide thin film deposited on GaAs substrate by e-beam evaporation has been carried out using non-destructive soft x-ray reflectivity (SXR) technique. The compositional details of the film are quantitatively estimated from the best fit of the optical constant profile derived from SXR measurements over 55-150 angstrom wavelength region. The SXR analysis reveals the film composition as 60% ZrO2, 20% Zr0.8O2.2 & 20% oxygen. The interface layer formed at film/substrate interface region is found to be comprised of 25% Ga2O3, 20% As2O3, 35% ZrO2 and 20% oxygen phases. (C) 2017 Elsevier B.V. All rights reserved.