Abstract: The partition function of nitrogen molecules are studied systematically in the temperature range of100- 6000
K. The molecular vibration, being taken as harmonic oscillator and non-harmonic oscillator partition function, is subjected to discussion, and the molecular vibration, being taken as the rotation partition functions of a rigid rotor, a vibrating rotor and other approximations, is also studied. The results show that the method for calculating the internal partition function by aid of approximation of non-harmonic oscillator and the vibrating rotor is the most accurate. And the accurate partition function val- ues of nitrogen molecules are also obtained in the range of100- 6000 K.