  We study the validity of the generalized second law (GSL) of gravitational
thermodynamics in a non-flat FRW universe containing the interacting in $f(T)$
gravity. We consider that the boundary of the universe to be confined by the
dynamical apparent horizon in FRW universe. In general, we discuss the
effective equation of state, deceleration parameter and GLS in this framewok.
Also, we find that the interacting-term $Q$ modifies these quantities and in
particular, the evolution of the total entropy, results in an increases on the
GLS of thermodynamic, by a factor $4\pi\,R_A^3\,Q/3$. By using a viable $f(T)$
gravity with an exponential dependence on the torsion, we develop a model where
the interaction term is related to the total energy density of matter. Here, we
find that a crossing of phantom divide line is possible for the
interacting-$f(T)$ model.
