  For an asymptotically flat hairy black hole in the Einstein-Maxwell-scalar
(EMS) theory, we study the possibility of shedding off its scalar hair via
nonlinear scalar perturbation fully interacting with the background spacetime.
We examine the effect of the perturbation strength on the descalarization. The
results show that the effective charge to mass ratio of the black hole plays
the key role in the dynamical descalarization. The descalarization at the
threshold is continuous. This indicates a second order phase transition.
