Multi-reference configuration interaction (MRCI) approach with Davison size-extensivity correction (+Q) is employed to calculate the potential curves and dipole moments of X^1\Sigma _\rmg^ + ,a^\prime ^1\Sigma _\rmu^ - ,a^1\Pi _\rmg and b^1\Pi _\rm u electronic states of N₂. The spectroscopic constants and vibrational level spaceings are calculated and in excellent agreement with the available theoretical results and experimental data. Based on the calculated molecular structure parameters, the opacities of N₂ in a temperature range of 295–20000 K under a pressure of 100 atm (1 atm = 1.01×10⁵ Pa) are presented. The results demonstrate that the wavelength range of absorption cross sections are enlarged with the temperature increasing. Moreover, the cross sections are mainly dominated in the range of ultraviolet for the cases with temperature T < 5000 K, while the obvious population can be found in the infrared ranges for the cases with temperature T > 10000 K due to the contribution of the excited states. The influence of temperature on the opacities of nitrogen molecule are investigated in the present work, which can provide theoretical and data support for researches of astrophysics and nuclear weapons.