Simultaneously applying our newly modified INDO scheme, ab initio method and one of the best semiempiricaI MO methods PM3 to calculate the molecular orbitals of Monohalogenobenzenes. Comparing the calculated first to twelveth ionization potentials and MO characters with the observed values, all evidences prove that this new INDO model is quite reliable. The new calculated ionization values and the assignments of electron configurations of C_6H_5Br and C_6H_5l are given in the same time. Especially there is a new idea about the assignments of electron configurations of C_6H_5F.