  We obtain the Misner-Sharp mass in the massive gravity for a four dimensional
spacetime with a two dimensional maximally symmetric subspace via the inverse
unified first law method. Significantly, the stress energy is conserved in this
case with a widely used reference metric. Based on this property we confirm the
derived Misner-Sharp mass by the conserved charge method. We find that the
existence of the Misner-sharp mass in this case does not lead to extra
constraint for the massive gravity, which is notable in modified gravities. In
addition, as a special case, we also investigate the Misner-Sharp mass in the
static spacetime. Especially, we take the FRW universe into account for
investigating the thermodynamics of the massive gravity. The result shows that
the massive gravity can be in thermodynamic equilibrium, which fills in the gap
in the previous studies of thermodynamics in the massive gravity.
