  We show that the $d^{0}$ ferromagnetism with high Curie temperature ($T_c$)
can be achieved in the electron doped hydrogenated epitaxial graphene on some
certain SiC substrates through first-principles calculations. The pristine
systems are found to be a Mott insulator independent of SiC polytypes (2$H$,
4$H$ or 6$H$) which, however, play a significant role in the modulation of
magnetic interaction. Carrier doping enhances the ferromagnetic coupling due to
the double exchange mechanism and thus realizes the phase transition from
antiferromagnetism to ferromagnetism. A $T_c$ of around 400 K is predicted on
the 2$H$-SiC. We employ a non-degenerate Hubbard model to demonstrate how the
SiC affects the interfacial magnetism in intra-atomic Coulomb repulsion and
intersite hopping interactions.
