Adopting the self-consistent method to calculate the coefficient of molecular orbital (MO) field in a metal/insulator/metal (MIM) system under the effect of a static electric field, we obtain the result that the distribution of the MO coe fficient appears in the form of sine function. With increasing electric field, t he energy band shifts to the deep energy area, and the energy peaks separate fro m each other more evidently, and the overlap of hybrid states between the 3dm group atomic orbits constructing the current pass increases, which im prove s the power of charge transportation. This work provides the method for research ing the effect of surface plasmon and polariton on charge transportation.