Taking into consideration the changes of the geometric shielding effect in a molecule as the incident electron energy varies, a modification method of additivity rule model for total cross section calculations of electron scattering from molecules at intermediate and high energies, is presented. Employing the modified additivity rule model, the total cross sections for electron scattering from NO, N2O, NO2 and C2H6 are calculated over a wide energy range from 50 to 5000 eV by using the experimental results of electron scattering from atoms C, N, H and O. The calculated values of total cross sections are compared with those obtained by measurements and other theories wherever available, and good agreement is attained over a wide energy range. It is shown that the total cross sections obtained by the modified additivity rule model are much closer to the measurements than the unmodified one and other theories. And it is also shown that the modification of complex optical potential must be related with energy of incident electrons so that the potential for total cross section calculations of electron scattering from free atoms is made suitable for the total cross section calculations of electron scattering from the ones in the molecule.