Abstract: A differential equation of the mass of system with negative heat capacity in background radiation, for example Schwarzschild black hole,is obtained ignoring an underlying unitary theory. A necessary study and discussion on the equation, mentioned in《Mechanics of new concept physics》, and《Heat of new concept physics》 are made. At the end a numerical simulation of the mass evolvement is carried out using Runge-Kutta method. It helps students understand the system with negative heat capacity more easily.

Key words: black hole, background radiation, heat radiation, Runge - Kutta method, numerical simulation.