This paper describes the synthesis and thermal behavior of 1.7-diamino-1,7-dinitrimino-2,4,6-trinitro2,4,6-triazaheptane (APX). The non-isothermal kinetics of APX was calculated by using the differential isoconversional method based on thermo-gravimetric/differential thermal analyzer results. It was found that with the extent of conversion increase, the activation energy increase from 136.6 kJ/mol to the highest value of 294.0 kJ/mol at the conversion of 40%, and then decrease to 248.2 kJ/mol; In addition. the decomposition mechanism of APX was systematically studied by in situ pyrolytic Fourier transform infrared spectroscopy, electron impact ionization analysis and density functional theory. The final decomposition products of APX were conformed to include N2O, NO2, CONH, H2CO, etc. The lowest bond dissociation energy of APX is N-N bonds and these may be decomposed initially. Finally, the most probable decomposition pathway based on the N6-N7 bond homolysis was proposed and the theoretical results are in good agreement with experimental data. (C) 2012 Elsevier B.V. All rights reserved.