We propose a theoretical method for analysis of resonant X-ray emission spectra from ab initio molecular orbital calculation using the single configuration approximation as an intermediate state. The method serves us a new possibility to simulate both resonant and non-resonant X-ray emission spectra. We also found out an interpretation that a peak at around 277 eV in the resonant spectrum of benzene molecule is due to the symmetry breaking of the core level. (c) 2006 Elsevier B.V. All rights reserved.