The relation between a black hole and a general black body system

Taking a black hole as a black body system, using general black body radiation theory, a Schwarzschild black hole and a Kerr–Newman black hole are investigated respectively. It is concluded that a black hole can be regarded as an ideal general black body system exactly for the changing process only. However, a stationary global black hole cannot be smoothly regarded as a general black body system. A black hole has some special characteristics which different from a general thermodynamics system. This conclusion means that a black hole should be inherently dynamical, at least when it is taken as a black body system.