system from ordered nonequilibrium state to disordered equilibrium state is demonstrated. It is also proved

that when the system is in equilibrium，the distribution of particles number satisfies the Boltzmann distribution. By

fitting the distribution curve，the temperature of this isolated system with known total energy at equilibrium state can

be obtained，and the fitting result is consistent with the following theoretical calculation. The relationship between

internal energy and temperature is further studied and it is proved that the equipartition theorem is valid in the high

temperature limit of the harmonic oscillator model.