There are two levels in the struoture of molecular crystals.The first level is molecule forming from atoms due to chemical bonds.The second level is crystal forming from molecules due to van der Waals forces.The structure characteristics of molecular crystals determine the characteristics of electronic energy bands.The band positions of the crystal orbitals are determined by the energy levels of the molecular orbitals; the widths of the bands and the state-densities are determined by the mutual action between the molecular orbitals belonging to the different molecules in the crystal.The relations between the energy bands of the crystal orbitals and the energy levels of the molecular orbitals and the atomic orbitals are shown in Fig.1.(All of the equations,tables and figures can be found in the Chinese Text).