  In this paper,we have studied phase transitions of higher dimensional charge
black hole with spherical symmetry. we calculated the local energy and local
temperature, and find that these state parameters satisfy the first law of
thermodynamics. We analyze the critical behavior of black hole thermodynamic
system by taking state parameters $(Q,\Phi)$ of black hole thermodynamic
system, in accordance with considering to the state parameters $(P,V)$ of Van
der Waals system respectively. we obtain the critical point of black hole
thermodynamic system, and find the critical point is independent of the dual
independent variables we selected. This result for asymptotically flat space is
consistent with that for AdS spacetime, and is intrinsic property of black hole
thermodynamic system.
