The scattering matrix approach to analyze the recurrence spectra of diatomic molecules in strong external magnetic field in the energy range E=77010—77050cm-1 is investigated. A new potential model is introduced to simplify the potential of the Rydberg electron of NO in external field. Based on the calculation of semiclassical orbits for the Rydberg states with rotation quantum number N=1,3,5, the long-range scattering matrix elements are obtained, which demonstrates that the quantum resonance peaks are intimately related to the corresponding closed orbits.