Through theoretical calculation and experimental data, the decomposition mechanism of the N,N'-azo azole poly-nitrogen compounds were obtained. The compounds with the decomposition caused by the rupture of the -N-N=N-N- bridge are more stable than the ones with the ring-opening decomposition mechanisms. The catenated -N-N=N-N- bridge can strengthen the stability of the nitrogen chain. Preventing the hybridization change of the N atom where the ring-opening reaction occurs is essential for the nitrogen chain elongation on the ring system. Moreover, the introduction of energetic substituents like nitro group can further improve the performances of poly-nitrogen compounds; and such a modification should be based on a stable poly-nitrogen backbone.