By using mean field theory and a perturbative canonical transformation

the ferromagnetism in the 3 dimensional Hubbard Hirsch model is investigated. It is shown that ferromagnetism only occurs when J ″>0 for small U or large U . For mediate value of U

the ferromagnetiam may or may not appear in the Hubbard model

and cannot be determined in the theory. The ferromagnetism regions are always smaller than that for half filling for a fixed J ″.