In the present work, we considered the contribution of the deep photoionization (photoionization of HOMO-1, HOMO-2, etc.) to better fit the experimental value, where the information of deep ionization energy was referred from the photoelectron spectroscopy as reported in the literature. Based on the deep ionization energy, the tota l photoionization cross-section is obtained by adding the photoionization cross-sections under each ionization channel, expanding single-channel to multi-channel. It should be noted that because of the indistinguishability of electrons and the Pauli principle, orbitals are not unique and unobservable. It means that it is not rigorous to regard photoelectrons as being in a specific orbit al before it is ionized. For the description of photoelectron behavior in photoionization, Dyson orbital is instead a more reasonable way. The Dyson orbital represents the difference between the electron-density distributions of the neutral molecule and its cation. Nevertheless, the concept of the molecular orbital is helpful for the analysis of some experimental phenomena.