The dynamic mechanical properties of NEPE propellant with minimum signature and its binder film were measured by dynamic mechanical analyzer. The results show that the mechanical loss (loss tangent and loss module) curves of the propellant and its binder film consist of α and β relaxations,which are caused by motion of the binder molecules and motion of plasticizer molecules associated with binder sidegroups,respectively. It is found that the magnitudes of tan δ (loss tangent) and loss modules of two relaxation processes of the propellant are obviously higher than those of the binder film because of the addition of nitramine in propellant. It is also found that viscoelastic coefficients from WLF equation and activation energy from relaxation processe of the propellant are lower than those of the binder film,which gives proofs that nitramine increases the free volume of the binder system and weakens the interactions of the molecular chains,further explains why the mechanical loss,tan δ,of the propellant is higher than that of the binder film.