  The interference phase of the high energy mass neutrinos and the low energy
thermal neutrons in a gravitational field are studied. For the mass neutrinos,
we obtain that the phase calculated along the null is equivalent to the half
phase along the geodesic in the high energy limit, which means that the correct
relative phase of the mass neutrinos is either the null phase or the half
geodesic phase.
  Further we point out the importance of the energy condition in calculating
the mass neutrino interference phase. Moreover, we apply the covariant phase to
the calculation of the thermal neutron interference phase, and obtain the
consistent result with that exploited in COW experiment.
