  In this paper we will apply the modified potential well method and
variational method to the study of the long time behaviors of solutions to a
class of parabolic equation of Kirchhoff type. Global existence and blow up in
finite time of solutions will be obtained for arbitrary initial energy. To be a
little more precise, we will give a threshold result for the solutions to exist
globally or to blow up in finite time when the initial energy is subcritical
and critical, respectively. The decay rate of the $L^2(\Omega)$ norm is also
obtained for global solutions in these cases. Moreover, some sufficient
conditions for the existence of global and blow-up solutions are also derived
when the initial energy is supercritical.
