In this report we present grazing incidence X-ray reflectivity (GIXR) study Of SiO2/Si(001) system. We have analysed the X-ray reflectivity data using recursive formalism based on matrix method and distorted wave Born approximation (DWBA). From the analysis of the reflectivity data we could obtain the electron density profile (EDP) at the interface of the dielectric SiO2 film and the Si(0 0 1) substrate. The EDP obtained from the matrix method follows the DWBA scheme only when two transition layers are considered at the interface Of SiO2/Si. The layer which is in proximity with the Si substrate has a higher electron density value than the Si and SiO2 values and it appears as a maximum in the EDP The layer which is in proximity with the dielectric SiO2 layer has an electron density value lower than the SiO2 value and it appears as a minimum in the EDP. When the thickness of the SiO2 layer is increased the lower density layer diminishes and the higher density layer persists. (c) 2006 Elsevier B.V. All rights reserved.