Abstract: Accurate characterization of the spectral radiative properties of N₂ molecules at high temperatures is of great significance for the design of thermal protection systems in entry missions to nitrogen-rich planetary atmospheres. Based on ab initio calculations, the spectral radiative properties of N₂ are systematically investigated under both local thermodynamic equilibrium (LTE) and non-local thermodynamic equilibrium (NLTE) conditions over a temperature range of 5 ~ 15000 K. The internally contracted multireference configuration interaction method with Davidson correction (icMRCI + Q), together with the augmented correlation-consistent polarized core-valence quintuple-zeta Douglas–Kroll basis set (aug-cc-pCV5Z-DK), is employed to compute the potential energy curves of 13 electronic states and the transition dipole moments of 7 transition systems, from which the partition functions, absorption/emission line intensities, cross-sections, and radiances are obtained, and the calculated absorption cross sections and spectral radiances show good agreement with the ExoMol database and NEQAIR results, respectively. The calculated results indicate that under LTE conditions, the \mathrmB^\prime ^3 \Sigma_\mathrmu^--\mathrmB^3 \Pi_\mathrmg , \mathrmW^3 \Delta_\mathrmu-\mathrmB^3 \Pi_\mathrmg and \mathrma^1 \Pi_\mathrmg-\mathrma^1 \Sigma_u^- transitions exhibit strong line intensities in the infrared waveband. The radiative features in the visible and near-infrared regions are collectively characterized by the \text B ^3 \Pi_\mathrmg-\mathrmA^3 \Sigma_\mathrmu^+ and \mathrma ^1 \Pi_\mathrmg-\mathrmw^1 \Delta_\mathrmu transitions, together with the low-frequency fronts of the \mathrmC^3 \Pi_\mathrmu-\mathrmB^3 \Pi_\mathrmg and \mathrmC^\prime ^3 \Pi_\mathrmu-\mathrmB^3 \Pi_\mathrmg transitions. Furthermore, the ultraviolet region is dominated by the \mathrmC^3 \Pi_\mathrmu-\mathrmB^3 \Pi_\mathrmg and \mathrmC^\prime ^3 \Pi_\mathrmu-\mathrmB^3 \Pi_\mathrmg transitions. In addition, comparisons between LTE and NLTE conditions reveal that under specific NLTE conditions, the absorption and emission cross-sections can be enhanced by up to several orders of magnitude compared with the LTE cases. Further analysis of different energy partitioning mechanisms under NLTE reveals that electronic energy, rather than vibrational-rotational coupling energy, dominates the radiative properties. Specifically, vibrational energy dictates the overall magnitude of the radiative intensity, whereas rotational energy primarily shapes the spectral band contours and rotational population distributions. This study, which addresses the frontier of high-temperature real gas effects, establishes a radiation property dataset that serves as a fundamental basis for thermal protection analysis and system design of high-speed vehicles.