Abstract: The charge densities, bond orders, free valences and the energies of n molecular orbitals of some l,4-bis[β-(4-Substituted phenyl) ethenyl] benzene and 1,4-bis [β-( 4-Substituted phenyl ) ethenyl 3-2,5-dimethoxy benzene compounds were calculated with HMOmethod. Arelationship of homologous linearity between the electronic spectra and the energy difference (HOMOand LUMO) is obtained. Besides, it was found that there is a relationship of homologous linearity between the electronic spectra and the absolute values of Hammett' sσp.