The determination of the energy level formula of molecular orbit and the determination of orbit coefficient formula by the method of solving the difference equation is presented.Concreta calculations have been made, taking straight chain conjugated olefins and monocyclic ring conjugated olefins as examples.The orbit coeflicienta is taken as a function of the code number q of an atom and this function is called the carrier wave of the molecular orbit,α=f(q) is used to represent the carrier wave.A difference eqnation is used to replace the simultaneous equations of the orbit.