A method of spectroellipsometric analysis to calculate the effects of inhomogeneous layers with arbitrary refractive index profiles along the surtace normal is proposed. The expressions presented by Charmet and de Gennes in 1983 are extended to include the effects of local perturbations around the interface inside both the substrate region and the ambient medium region. The first-order perturbation is considered and the solutions are given in terms of definite integrals. Computer calculations show that deviations of the Δ and ψ spectra increase in proportion to the total amount of local perturbations. The results are compared with those of the differential program and the conventional technique of simulation and the practicality of this method is discussed.