The electronic structure of an ionized high spin molecule, meta-triphenyl-dicarbene, is studied with a semi-empirical model for π and n electrons using the unrestricted Hartree-Fock (UHF) and resonating HF (Res HF) approximations. The calculated spin multiplicity of the ground state is quartet and the injected hole or electron is in the π system, which is consistent with the experiments. In the UHF approximation, it makes a SDW polaron localized around a carbene site. The Res HF approximation shows that a quantum motion of the SDW polaron between the two carbene sites and quantum fluctuations of its electronic structure more stabilizes the quartet state.