Abstract: By using the perturbation theory and Mathematica, the energy level splitting （ n = 3 - 7） of the hydrogen atom in the electric field and magnetic field of the same direction is calculated. The numerical results show that the degeneracy of energy levels （n = 3 -7 ） is completely removed in many cases, while the overall energy level splitting is not equidistant. But under certain conditions,the overall energy level splitting is equidisatnt, and the degeneracy of energy levels is not completely removed, the energy is only split into 3n-2 different levels. The result from some recent articles is not comperhensive.

Key words: hydrogen atom, electric field and magnetic field, perturbation theory, energy level splitting